Patent Application
20240401857
The present invention relates to a cooling system for cooling a component, for example for cooling a laboratory instrument. In particular, the present invention relates to a cooling system for use in laboratory instruments. Furthermore, the present invention relates to laboratory bench instruments, comprising but not limited to centrifuges, incubators, and biological safety cabinets.
It is known to provide cooling in laboratory instruments, for example in centrifuges, in order to cool components of the centrifuge (in particular the rotor chamber) or to control the temperature.
It is known to provide cooling systems in laboratory instruments that provide cooling of the component to be cooled via a refrigeration circuit in which, for example, a fluorinated refrigerant, in particular comprising R134a, R449A, R1234yf, R125, and/or R32, flows as a refrigerant and heat is transferred from the component to be cooled to the environment via aggregate changes.
Such cooling systems have proven successful, but have some disadvantages and shortcomings. In particular, such cooling systems are not particularly environmentally friendly, due to the refrigerant used.
In light of this, there is a need for laboratory instruments, and generally for cooling systems, which have improved environmental compatibility. It is an object of the present invention to overcome or at least mitigate the shortcomings and disadvantages of the prior art. In particular, it is an object of the present invention to provide a cooling system and a laboratory instrument with increased environmental compatibility, which ideally enables use in a wide ambient temperature range.
These objects are achieved by the cooling system of the present invention.
According to a first aspect, the invention relates to a cooling system. The cooling system has a refrigeration circuit comprising an evaporator, a compressor, a pressure reduction device, a gas cooler, and a line system. The line system connects the evaporator, the compressor, and the gas cooler to one another. Furthermore, the cooling system comprises a refrigerant in the refrigeration circuit and a cooling device, which is additional to the refrigeration circuit, for cooling the gas cooler.
By providing the additional cooling device for cooling the gas cooler, the invention allows refrigerants other than R134a to be used efficiently. For example, the present invention makes it possible to use CO2 as a refrigerant in such a way that the entire circulation process takes place in the subcritical range, which increases the efficiency of operation. In particular, embodiments of the present technology thus make it possible to use refrigerants that have a significantly reduced global warming potential compared to conventional refrigerants and thus improve the environmental compatibility of cooling systems.
Through the use of the additional cooling device, which can comprise, for example, a heat pump and in particular a thermoelectric converter, the present invention can contribute to cooling the refrigerant leaving the gas cooler to a lower compressor outlet temperature and/or realize a reduced mass flow of the refrigerant with an increased enthalpy difference via the evaporator. The latter can also bring about better volumetric efficiency of the refrigeration system and thus realize a higher refrigerating power with reduced drive power. In addition, the use of thermoelectric cooling of the refrigerant makes it possible to control the degree of refrigerant subcooling to a desired level depending on the system parameters, the ambient conditions, and the refrigeration requirements. On the basis of the lower temperature of the refrigerant, an improved service life of the compressor can be realized. An improved oil quality can advantageously be achieved with the lower refrigerant temperature and/or lower refrigerant pressures. This can also increase the service life of the components of the refrigeration circuit. In addition, a gas cooler can be selected which is specified for lower temperatures and/or lower pressures and is correspondingly simpler in design. In particular, the material and a material thickness of the gas cooler can be adapted.
The refrigeration circuit can absorb heat at the evaporator (and thus extract heat from the surroundings) and/or release heat at the gas cooler. In particular, the refrigeration circuit can be a closed refrigerant circuit. The cooling component can be a heat exchanger that is designed to thermally couple the refrigerant to a heat transfer medium in order to realize an efficient heat transfer from the refrigerant to the heat transfer medium. The refrigerant can be gaseous in the gas cooler and the heat transfer medium can also be gaseous.
The additional cooling device can in particular be designed as an open circuit in which ambient air is used as a heat transfer medium. Alternatively, a secondary refrigeration circuit can be provided as an additional cooling device.
The refrigeration circuit can have a multi-stage design. The advantage can thereby be achieved that particularly high pressures can be achieved. A gaseous refrigerant can be compressed sequentially by means of further compressors from a first pressure, via a plurality of intermediate pressures, to a final pressure. A further compressor can be provided for each intermediate compression. This allows the compression process to be distributed over a plurality of compressors.
The pressure reduction device can be an expansion valve. The expansion valve can be designed to be controllable in order to implement controllable pressure regulation, in particular a pressure reduction. The refrigerant can expand through the expansion valve.
The refrigeration circuit can be designed as a cascade. A cascade can be realized by a thermal coupling of two refrigeration circuits. Parts of the cascade can be thermally coupled in order to realize a heat transfer. Each cascade can have a separate cooling circuit. In particular, each partial refrigeration circuit can have a separate line system from the other circuits. The cooling capacity of the refrigeration circuit can be increased by cascading the refrigeration circuit.
The refrigeration circuit can have a two-stage design, wherein the refrigeration circuit has a further compressor and the compressor and the further compressor are designed to compress the refrigerant in two stages. In particular, a low-pressure compressor can be used to compress from a low pressure to a medium pressure. In addition, the refrigerant can also be cooled at the medium pressure. The refrigerant at the medium pressure can then be supplied to the compressor in order to further compress from the medium pressure to a high pressure.
The gas cooler can be arranged downstream of the compressor and/or the further compressor in the direction of flow of the refrigerant.
The gas cooler can be a liquefier.
The refrigerant can be carbon dioxide (hereinafter also abbreviated as CO2 or R744). R744 can have low toxicity. When R744 is used, the refrigeration circuit can pass through a transcritical cycle: the critical point can be exceeded. As a result, a pressure and/or a temperature at the compressor can be increased. Due to the low critical temperature of CO2 and the shape of the isotherms around the critical point, the performance of the gas cooler may be limited by the temperature of the ambient air.
The thermodynamic performance of a transcritical CO2 cycle can be lower than the thermodynamic performance of a comparable cycle with conventional coolants in a subcritical cycle. However, a performance number of the CO2 cycle can be higher due to higher compressor efficiency and better transport characteristics. The performance number can reflect the ratio of refrigeration power generated to power consumed.
An additional cooling of the refrigerant can be implemented to improve the cooling performance when R744 is used in the refrigeration circuit. In particular, a cooling can be realized by means of the additional cooling device. Advantageously, the additional cooling device is designed to extract heat from the refrigerant at the gas cooler, more preferably at an outlet of the gas cooler.
The additional cooling can alternatively be realized by means of a heat exchanger integrated in the primary circuit. However, a quantity of overheating entering the compressor may thereby be increased, so that a lower refrigerant density and/or a higher temperature may occur at a compressor outlet.
The additional cooling device can be used for energetic optimization of the refrigeration circuit at higher ambient temperatures, in particular at ambient temperatures above 25° C., more preferably at ambient temperatures above 28° C. The cooling system can be used in medical devices, in particular in centrifuges, which can be operated up to an ambient temperature of 40° C. Depending on the temperature, the optimum high pressure can also increase. Furthermore, a performance number of the refrigeration circuit may depend on reaching the optimum high pressure. If the temperature and pressure values exceed a critical point of the refrigerant, the heat dissipation process can run transcritically as gas cooling. A transcritical gas cooling can take place isobarically but not isothermally. Liquefaction, on the other hand, can take place isobarically and largely isothermally. Due to the increased pressure of a transcritical gas cooling, a drive power of the compressor can be increased.
By cooling the refrigerant (by the additional cooling device), an optimal high pressure of the refrigerant can be reduced. In particular, the optimal high pressure can be a function of the gas cooler outlet temperature. With the cooling of the refrigerant, an energetically favorable liquefaction can be achieved. Cooling at the gas cooler can also be achieved using primary energy, i.e., the refrigeration capacity of the refrigeration circuit. An increase in efficiency of the overall process can be achieved by a further primary energy saving at another location: in a subcritical process, a required drive power of the compressor can be lower than in a transcritical process. Due to the reduced drive power of the compressor, primary energy in the form of electricity can be saved here.
The refrigeration system can be designed to perform a transcritical vapor compression cycle. In a transcritical cycle, the refrigerant can be above a critical point of the refrigerant, at least at times or in parts of the cycle. In particular, part of the cycle can occur at pressures above the critical point and another part of the cycle at pressures below the critical point. The critical point can mark the upper limit for heat transfer processes based on evaporation or condensation. At temperatures and pressures above this critical point, the refrigerant exists as a supercritical fluid; a separate gaseous phase and a separate liquid phase no longer exist. For example, to the left of the critical point, towards lower enthalpies, the refrigerant can have a density comparable to the liquid phase but is in the gaseous phase.
The heat extracted from the refrigerant at a gas cooler outlet through the gas cooler ensures an increased cooling effect: a correspondingly higher amount of heat can be absorbed at the evaporator. The refrigeration cycle can have a specific cycle performance characteristic that corresponds to a preferred operating state point at which the cooling system operates at optimal cycle efficiency. The additional cooling device can achieve the advantage that, in the event of a deviation from this operating state point, readjustments can be made accordingly in order to achieve optimal system efficiency. The regulation here comprises in particular the adaptation of the cooling capacity of the additional cooling device.
The cooling system can have a refrigeration capacity in the range of 10 W to 100 KW, preferably in the range of 500 W to 10 KW. Accordingly, the refrigeration cycle can be scaled in a range from small mobile devices and benchtop laboratory instruments to large industrial systems.
The refrigeration cycle can be designed to perform a subcritical vapor compression cycle. A refrigerant cycle that is completely below the critical point can be referred to as a subcritical refrigerant cycle. In subcritical circuits, the refrigerant can be condensed, i.e., the compressor outlet pressure can be lower than the critical pressure. In particular, a high-pressure side of the refrigeration circuit can operate below a critical pressure. In a log (p)-h diagram (pressure-enthalpy diagram), the representation of a subcritical CO2 cycle can be qualitatively similar to other refrigerants. Only the pressure values and the evaporation and condensation temperatures can vary. The use of a completely sub-critical circulation process can be advantageous, since this can improve the system efficiency and the cooling performance compared to a transcritical process.
The gas cooler can be a heat exchanger, in particular a radiator. This allows heat from the refrigerant to be removed from the refrigeration circuit. In particular, the heat exchanger can realize a heat transfer without material transfer. The refrigerant can flow in the line system so as to be insulated and/or sealed from an ambient atmosphere. Here the term “flow” is used equally for gases and liquids. In particular, flowing can also be understood as streaming.
The gas cooler can be a microchannel heat exchanger or a fin-and-tube heat exchanger. A surface for heat dissipation can thereby advantageously be maximized. A line through which the refrigerant flows can be connected to cooling fins in order to dissipate heat from the refrigerant via the line and the cooling fins. A microchannel heat exchanger can have an increased heat transfer coefficient and an enlarged heat transfer surface.
The gas cooler can be designed to cool the refrigerant by means of heat dissipation into the ambient air. A surrounding atmosphere can thereby be used as a heat sink. Furthermore, the refrigerant can flow through the gas cooler completely in a gaseous phase. With a gaseous ambient atmosphere, the gas cooler can be a gas-gas heat exchanger that is designed to transfer heat from a first gas, the refrigerant, to a second gas, the surrounding atmosphere.
The gas cooler can be designed to cool the refrigerant to a temperature which is in a range which is limited upwards by the ambient temperature plus 3 K. Without active cooling of the gas cooler, the temperature of the refrigerant can always be higher than the ambient temperature in order to ensure heat transfer from the refrigerant to the ambient atmosphere. Depending on the dimensioning of the gas cooler, the temperature difference can vary.
The gas cooler can be designed to cool the refrigerant to a temperature below 31° C., preferably to cool it to below the critical temperature of 30.98° C., further preferably to below 30° C. This has the advantage that when CO2 is used as a refrigerant, it remains below a critical point. Alternatively, a safety distance of up to 5 K from a critical temperature of the refrigerant can be provided. The temperature difference to the critical temperature can be adjusted according to the measurement and/or control accuracy of the cooling system. The more precisely a control can be realized, the smaller the distance to a critical temperature can be set.
The gas cooler can have a gas cooling line which is designed to conduct the refrigerant. Accordingly, the refrigerant flows through the gas cooling line. The gas cooling line can be arranged in loops so that the length of the gas cooling line and correspondingly the flow time of the refrigerant in the gas cooler is increased.
The gas cooler can have a cooling surface which is arranged on the gas cooling line, wherein the heat transfer medium flows along the cooling surface in order to remove heat from the cooling surface. In particular, the gas cooler can be a microchannel gas cooler or a fin gas cooler. The microchannel gas cooler can have a plurality of parallel channels through which the refrigerant flows.
The additional cooling device can comprise a Peltier element. Electrical power can be used to extract heat from the refrigeration circuit, particularly at the gas cooler. The additional cooling device can comprise an air-to-air heat exchanger which is designed to generate cold air. An air flow can be cooled at a first heat sink. This cold air can then be conducted insulated from the remaining ambient atmosphere in order to cool the gas cooler. The cold air can flow through the gas cooler in order to absorb heat from the refrigerant flowing in the gas cooler. A control of the refrigeration circuit can be independent of a control of the additional cooling device. The additional cooling device can be arranged in such a way that an air flow to the refrigeration circuit substantially passes completely through the additional cooling device. Accordingly, the additional cooling device has the effect of an adjustment of the ambient temperature to the refrigeration circuit. The control of the additional cooling device can accordingly be designed such that a temperature of the cold air flow is always low enough to ensure a subcritical state of the refrigerant in the gas cooler.
The additional cooling device can be thermally coupled to the refrigeration circuit to extract heat from the refrigerant. A coupling can here be realized via an air flow from the additional cooling device to the gas cooler. Furthermore, a heat sink of the additional cooling device can be arranged on the refrigeration circuit, in particular on the gas cooler.
The additional cooling device can comprise a heat pump. In particular, the heat pump can supply heat to the ambient atmosphere and extract heat from the refrigeration circuit. The heat pump can comprise at least one thermoelectric converter. In particular, the thermoelectric converter can have a homogeneous surface temperature. With the thermoelectric converter, the refrigerant can be transferred into the wet vapor range. The at least one thermoelectric converter can in particular also be a plurality of thermoelectric converters. The use of a plurality of thermoelectric converters can lead to increased efficiency. Thermoelectric energy conversion can be a direct conversion of thermal energy into electrical energy, in particular in a solid body. It should therefore be understood that in the sense of the present document, for example, arrangements which pump heat from a cold point to a warm point by means of a Peltier element are also understood to be heat pumps.
Thermoelectric converters can use semiconductor materials to remove heat by using electrical energy, through the Peltier effect. A typical thermoelectric converter comprises an arrangement of p- and n-type semiconductor elements. If an electrical current flows through one or more pairs of elements, a temperature drop occurs at the connection point, the cold side, which leads to the absorption of heat from the environment. The heat is transported by electron transport through the thermoelectric converter and released on the opposite warm side when the electrons move from a high to a low energy state.
The heat pump can further comprise a plurality of thermoelectric converters. In particular, the number of thermoelectric converters can scale with the cooling capacity of the refrigeration circuit; in particular, the number of thermoelectric converters can be a multiple of the required amount of heat. In particular, the total refrigeration capacity of the heat pump can thereby be scaled. Furthermore, a surface geometry can be adapted to an installation location of the thermoelectric converters. For example, the thermoelectric converters can be arranged in a plane adjacent to or spaced apart from one another. The thermoelectric converters can also be arranged offset relative to one another.
Each of the at least one thermoelectric converters can have a cooling capacity of 1 W to 1 KW, preferably 1 W to 100 W, more preferably 60 W. The advantage of a sufficient cooling capacity can thereby be achieved. Furthermore, it can be advantageous to operate a plurality of thermoelectric converters with a lower electrical power than the corresponding maximum power in order to distribute the refrigerant power to a larger area. The number of thermoelectric converters to be used can be selected with respect to a corresponding cooling surface, a maximum power, a maximum temperature rise and/or an ambient temperature range. Furthermore, the selected number of thermoelectric converters can be selected such that a cooling capacity can be maximized with the coupling to a heat sink.
Each of the at least one thermoelectric converters can be a Peltier element. The cooling effect of the Peltier element can be stronger the better the heat can be dissipated from the one side of the Peltier element, i.e., the lower the temperature difference between two sides of the Peltier element.
A performance number of the Peltier element can drop with a higher temperature difference between a cold side and a warm side of the Peltier element. Advantageously, a temperature difference between 10 K and 20 K can be selected. In this range, the performance number can be in a range of 1.5 to 2.75. In other words, for 1 W of electrical power supplied to the Peltier element, 1.5 W to 2.75 W of refrigerating power is generated. Accordingly, the optimum high pressure for an ambient temperature of 40° C. with a difference at the Peltier element of 20 K can be approx. 57 bar. A liquefaction of the refrigerant can thus be achieved. A gas cooler outlet temperature can be around 43° C., especially in a typical gas cooler design, without provision of the additional cooling device or a Peltier element. The optimal high pressure could be about 100 bar. By reducing the gas cooler outlet temperature to 23° C., the optimum high pressure can be shifted to a subcritical range, for example to 57 bar.
Each of the at least one thermoelectric converters can be arranged at a distance from the refrigeration circuit, or on the refrigeration circuit. With a spaced arrangement of the thermoelectric converters, a heat transfer medium can be used to thermally couple the thermoelectric converters to the refrigeration circuit. Here, the heat can be dissipated in particular by flowing of the heat transfer medium, i.e., convectively. Furthermore, heat can also be dissipated in part via thermal radiation. Alternatively, the thermoelectric converters can be arranged on the refrigeration circuit and connected to an element of the refrigeration circuit, in particular with a force-fit connection, at least partly with a positive fit and/or a non-positive fit. In this way, the heat can be removed from the refrigeration circuit by means of heat conduction.
Each of the at least one thermoelectric converter can be arranged on the gas cooler, in particular at an inlet and/or at an outlet of the gas cooler. The advantage can thereby be achieved that heat can be extracted from the refrigerant from a portion of the refrigeration circuit at maximum temperature. Furthermore, the cooling capacity of the gas cooler can scale with the temperature difference between the refrigerant and the heat transfer medium. Accordingly, it can be advantageous for the gas cooler to cool the refrigerant using the ambient air as the heat transfer medium and for the heat pump to further cool the refrigerant at an outlet of the gas cooler.
The at least one thermoelectric converter can be arranged on the line system. Furthermore, a plurality of thermoelectric converters can be arranged at different points of the line system. In particular, a cooling of the refrigerant in the line system can be achieved thereby.
The heat pump can have a cold side and a warm side, wherein the heat pump is designed to transport heat from the cold side to the warm side. Accordingly, the waste heat can be removed from the system at the warm side.
The additional cooling device can comprise a heat transfer medium. The heat transfer medium can also flow in a closed circuit or be formed by an external heat transfer medium reservoir, for example a central cooling system. In addition, the ambient atmosphere can be used as a heat transfer medium. The gas cooler can be initially designed to cool the refrigerant by a flow of the heat transfer medium through the gas cooler. The additional cooling device can advantageously lower a temperature of the heat transfer medium before entry into the gas cooler in order to increase the cooling capacity of the gas cooler.
The additional cooling device can have a transport device which is designed to thermally couple the refrigeration circuit and the heat pump by means of the heat transfer medium. The transport device can also be referred to as a heat transfer medium transport device. The transport device can transport the heat transfer medium from the heat pump to the cooling circuit in order to realize a convective heat exchange. The transport device is advantageously arranged in such a way that a volume flow of the heat transfer medium through the gas cooler is maximized. The transport device can suck and/or blow a stream of air through the gas cooler. For simultaneous suction and blowing, the transport device can include two ventilators. Advantageously, the transport device is arranged on the inside of the gas cooler. The inside can have a surface normal that points in the direction of the interior of the instrument. The transport device can comprise a pump and/or a ventilator. The transport device can be designed to generate a flow of the heat transfer medium to the refrigeration circuit.
The transport device can also be designed to generate a flow of the heat transfer medium along a surface of the gas cooler and/or through the gas cooler. In particular, a volume flow of the heat transfer medium can be controlled by the conveying capacity of the transport device. Accordingly, the cooling capacity of the gas cooler can be influenced by adjusting the power of the transport device. The refrigerating capacity of the heat pump and the delivery rate of the transport device can define the achievable cooling of the refrigerant in the gas cooler. In addition, the coupling efficiency of the heat pump to the heat transfer medium can also influence the cooling capacity in the gas cooler.
The transport device can be arranged on a side of the gas cooler facing away from the heat pump, on a side of the gas cooler facing the heat pump, on the cold side, on the gas cooler, and/or between the heat pump and the gas cooler. In particular, the transport device is arranged in such a way that a flow resistance of the heat transfer medium through the gas cooler can be minimized. Appropriate channels and/or conducting devices can be provided to conduct the heat transfer medium to the gas cooler. In particular, a flow of the heat transfer medium can be separated from the ambient atmosphere. Here the heat transfer medium can be defined as an air flow that is separated from the ambient atmosphere by appropriate air conducting devices. For example, an air inlet on the heat pump can form the inlet point for the heat transfer medium. Furthermore, the air duct can be supplemented by an external hose system, for example to draw in air volumes from a distance away, rather than the immediate ambient air.
The transport device can be designed to form a flow direction, in particular a suction direction, in the heat transfer medium which is directed from the heat pump in the direction of the gas cooler. The flow direction can furthermore be changed by corresponding structures in order to optimize an entry of the heat transfer medium into the gas cooler. In particular, the heat transfer medium can flow along a rear side of the instrument and then flow in a laminar fashion through the gas cooler in the direction of the front of the appliance.
The transport device can be designed to guide the heat transfer medium at least partially along the cold side. The heat transfer medium can thereby emit heat to the heat pump, so that a temperature of the heat transfer medium can be lowered. The temperature of the heat transfer medium can be adjusted in such a way that the refrigerant is always below a critical point, taking into account the cooling capacity of the gas cooler.
The transport device can be designed to generate a flow of the heat transfer medium through the heat sink, through a heat transfer medium chamber and/or through the gas cooler along the cooling surface. A flow velocity can be adapted such that a heat absorption at the gas cooler and a heat dissipation at the heat pump is maximized by the heat transfer medium. Accordingly, the flow cross sections at the heat pump or the heat sink and at the gas cooler can be of different sizes in order to realize different flow velocities with the same volume flow.
The heat transfer medium can be designed to thermally couple the heat pump, in particular the cold side, and the refrigerating circuit. In particular, the heat transfer medium can be designed to thermally couple the heat pump and the gas cooler. Advantageously, heat losses of the heat transfer medium to the surroundings between the heat pump and the gas cooler are reduced. This can be realized by keeping the flow paths of the heat transfer medium between the heat pump and the gas cooler as short as possible.
The heat transfer medium can be non-flammable, non-toxic and/or free of halogenated hydrocarbons; in particular it can be air or water. In particular, a high compatibility with existing refrigeration systems, for example central water cooling devices or climate-controlled laboratories, can thereby be provided. Furthermore, a corresponding exchange with the surroundings is harmless. The heat transfer medium can be materially insulated from the refrigerant so that only a thermal coupling can be present here. Accordingly, the heat transfer medium can be formed by the ambient atmosphere. In this case, the additional cooling device can detect parameters of the ambient atmosphere, for example a temperature, a pressure and/or an air humidity, in order to detect the thermal properties of the ambient atmosphere in its effect as a heat transfer medium and to control the additional cooling device accordingly. For example, the heat capacity of the heat transfer medium can scale with the pressure and/or with the air humidity. The heat pump can be designed to cool the heat transfer medium; in particular, a defined reduction in the temperature of the heat transfer medium at an inlet of the heat pump to an outlet of the heat pump can be achieved. In this case, a heat pump inlet can be defined as an inflow surface of a heat sink which is coupled to the cold side. Furthermore, a heat pump outlet can be defined as an outflow surface of the heat sink, through which the heat transfer medium flows away from the heat pump.
The additional cooling device can be designed to cool the heat transfer medium, in particular by means of the heat pump, preferably to a temperature below 31° C., in particular below 30.98° C., more preferably to a temperature below 27° C. The temperature to be achieved can be determined depending on a minimum temperature difference which the gas cooler can reach between the refrigerant and the heat transfer medium. For example, the gas cooler can have a minimum achievable temperature difference of 3 K, so that at a temperature of 27° C. of the heat transfer medium, a temperature of 30° C. of the refrigerant can be achieved. This can be sufficient to prevent a transition of the refrigerant into a critical state. In particular, a safety distance can be defined here so that local temperature fluctuations in the gas cooler also prevent the critical point from being exceeded locally.
The additional cooling device can comprise a secondary heat transfer medium. With the secondary heat transfer medium, heat absorbed from the heat transfer medium by the heat pump can be removed by the heat pump. The secondary heat transfer medium can be formed by a separate flow of the ambient atmosphere. Here, the secondary heat transfer medium can flow along the warm side due to a temperature difference between the warm side and the ambient atmosphere, in order to remove heat.
The additional cooling device can furthermore comprise a secondary transport device which is designed to generate a flow in the secondary heat transfer medium in order to cool the heat pump. A flow of the secondary heat transfer medium opposite a natural convection direction can thereby be generated, for example. This can realize the advantage that a flow of the secondary heat transfer medium is aligned parallel to a flow of the heat transfer medium. A heat input into the heat transfer medium can thus be reduced by a flow of the secondary heat transfer medium. In other words, the air flow, which cools the warm side of the heat pump, can first emit the absorbed heat to the ambient atmosphere and not directly transition into a flow of the heat transfer medium. Here, heat input into the air flow along the cold side would lead to a reduction in the refrigerating capacity of the heat pump. Furthermore, the fluid that is to be cooled can be cooled below the heated outlet temperature of the cold fluid by means of a counterflow guiding. With a flow guided in the same direction, the outlet temperature of the warm fluid cannot reach the outlet temperature of the cold fluid, even with a heat exchanger of any length.
Accordingly, the secondary transport device can be arranged at the warm side. The transport device can be arranged in such a way that a flow of the secondary heat transfer medium after flowing through a heat sink on the warm side has as little material exchange as possible with a flow of the heat transfer medium before flowing to the cold side.
The secondary transport device can comprise a pump and/or a ventilator. A plurality of ventilators can be provided, which are arranged on the heat sink, in particular at an outlet surface of the heat sink through which the heated secondary heat transfer medium flows.
The secondary heat transfer medium can be formed by the ambient atmosphere. In particular, the ambient atmosphere can be divided into two separate streams at the heat pump, wherein a first stream forms the heat transfer medium and a second stream forms the secondary heat transfer medium. A flow rate of the heat transfer medium can be adapted to a flow rate of the secondary heat transfer medium (and vice versa) in order to prevent mixing of the heat transfer media before the heat pump, i.e., upstream of the heat pump. Furthermore, the heat transfer medium and the secondary heat transfer medium can be separated from one another by a separating wall upstream of the heat pump.
The secondary transport device can be designed to generate a flow of the secondary heat transfer medium at the warm side, in particular along a surface of the warm side. As a result, the secondary heat transfer medium can absorb heat from the warm side and transport away it in order to remove heat from the heat pump.
The additional cooling device can have a separating wall which is designed to separate the heat transfer medium and the secondary heat transfer medium. The separating wall can separate the heat transfer medium and the secondary heat transfer medium downstream of the heat pump. Furthermore, a corresponding separation can also be realized upstream of the heat pump at least for a limited portion. The separating wall can realize not only a material separation of the heat transfer medium from the secondary heat transfer medium. In addition, a thermal decoupling can also be realized on the basis of corresponding thermally insulating properties of the separating wall.
The separating wall can be arranged in the same plane as the heat pump. The heat transfer medium and/or the secondary heat transfer medium can thereby flow along the separating wall with low flow resistance.
The separating wall can have a receptacle for the heat pump. The receptacle can be formed by a depression or a recess in the separating wall. In particular, the cold side and/or the warm side of the heat pump can terminate flush with the separating wall.
The separating wall can be arranged at the warm side. For example, a rear side of the separating wall can be designed to absorb heat from the warm side and release it into the ambient atmosphere. The separating wall can be a sandwich panel which has thermally insulated surfaces. The cold side can be thermally coupled to a surface facing the gas cooler and/or the warm side can be thermally coupled to a surface facing away from the gas cooler. Accordingly, the separating wall can be designed to absorb heat from the heat transfer medium and/or to emit heat from the secondary heat transfer medium.
The separating wall can be designed to direct the flow of the heat transfer medium in such a way that the heat transfer medium flows through the gas cooler. In particular, the heat transfer medium can flow into a heat transfer medium chamber formed by the separating wall, and from the pre-chamber into the gas cooler. This can be used, for example, to change the surface content of an inflow surface and the flow direction of the heat transfer medium. In this case, the heat transfer medium can flow along the cold side of the heat pump at a first flow rate and through the gas cooler at a second flow rate. The first flow rate can be greater than the second flow rate. In addition, a first flow direction can be oriented perpendicular to a second flow direction, wherein the first flow direction can be defined by the first flow rate and the second flow direction can be defined by the second flow rate. Here the heat transfer medium is advantageously gaseous, flows along the heat pump, and is then directed toward the gas cooler in order to flow through it.
The separating wall can be thermally insulated from the heat pump. Accordingly, a heat exchange between the heat pump and the separating wall can be prevented. A heat exchange can thus be limited to a precisely defined heat sink surface.
The additional cooling device can comprise a heat transfer medium chamber. The heat transfer medium chamber can fluidically couple the cold side of the heat pump and the gas cooler or can be arranged between the heat pump and the gas cooler. The heat transfer medium chamber can in particular achieve a homogenization of a flow of the heat transfer medium after the heat pump. A laminar flow to the gas cooler can be realized here, for example. Accordingly, the heat transfer medium chamber can be filled with the heat transfer medium.
The heat transfer medium chamber can be designed to distribute a refrigerant flow of the heat transfer medium onto the cooling surface of the gas cooler. Advantageously, the heat transfer medium chamber is fluidically coupled to the gas cooler in such a way that an inflow surface of the gas cooler is completely covered by an outlet opening of the heat transfer medium chamber in order to enable a uniform flow to the gas cooler.
The heat transfer medium chamber can be designed to fluidically and/or thermally insulate the heat transfer medium from the secondary heat transfer medium. A heat transfer between the heat transfer medium and the secondary heat transfer medium can thereby be prevented.
The separating wall can at least partially close off the heat transfer medium chamber. In particular, an outflow of the cooled heat transfer medium can thereby be reduced, so that a volume of heat transfer medium downstream of the heat pump flows substantially completely through the gas cooler.
The additional cooling device can comprise a first heat exchanger. The heat exchanger can be designed to improve a thermal coupling of the cold side and the heat transfer medium. In particular, the heat exchanger can conduct heat from the heat transfer medium to the cold side and can effectively enlarge the surface of the cold side by a surface of the heat exchanger. A contact surface of the cold side with the heat transfer medium can be increased in this way.
The first heat exchanger can be a heat sink. The heat sink can have cooling fins which are perforated at least partially along a flow direction of the heat transfer medium. Advantageously, the cooling fins are aligned along the flow direction of the heat transfer medium. A flow resistance of the heat sink in relation to a flow of the heat transfer medium can thereby advantageously be reduced.
The first heat exchanger can be extruded and made of aluminum or an aluminum alloy. In particular, this allows a high thermal conductivity and a high heat transfer coefficient on the air side (e.g., a factor of 3 higher than when using a copper pipe and fin) to be achieved in order to extract heat from the heat transfer medium by means of the heat pump or the at least one thermoelectric converter.
The first heat exchanger can be formed by an aluminum body which is milled and/or is a die-cast aluminum body. This allows any structure to be efficiently incorporated into the aluminum body in order to create the largest possible cooling surface. The heat sink can be in one piece and designed for contact with a plurality of thermoelectric converters. For this purpose, in particular a base surface of the first heat exchanger can have receptacles for the cold surfaces of the thermoelectric converters. Alternatively, the base surface can be flat.
The gas cooler can be arranged at least partially in the first heat exchanger. The first heat exchanger can, for example, form a portion of the cooling fins of the gas cooler. Accordingly, the heat can be transported by the refrigerant to the cold side of the heat pump by means of heat conduction. In general, the first heat exchanger can be connected to the gas cooler at least in part by a force-fitting, materially bonded, and/or positively-fitting connection.
The first heat exchanger can have a recess in which the gas cooling line is at least partially arranged. A heat conduction from the refrigerant to the heat pump can thus be efficiently realized. The first heat exchanger can be arranged on a first partial portion of the gas cooling line, which is arranged upstream of an air cooling element of the gas cooler, or on a second partial portion of the gas cooling line, which is arranged downstream of the air cooling element of the gas cooler. It will be clear to those skilled in the art that the term gas cooling line does not exclude the refrigerant being present as a liquid, which is the case for example when there is cooling to below the boiling point (30.98° C. in the case of CO2).
The cold side can be connected to the first heat exchanger, for example glued, welded, screwed or connected by means of an adhesive heat medium conducting layer, so that a surface of the first heat exchanger forms the cold side. For example, the surface of the heat exchanger can form a surface of the cold side with respect to an interaction with the transport device.
A plurality of thermoelectric converters can be arranged on the separating wall and/or the first heat exchanger can be arranged in the heat transfer medium chamber. For example, the first heat exchanger can extend from the cold side of the corresponding thermoelectric converter at least partially into the heat transfer medium chamber.
The first heat exchanger can be formed by a plurality of primary heat sinks and a first group of thermoelectric converters of the plurality of thermoelectric converters can in each case be arranged with the cold side on a first heat sink of the plurality of primary heat sinks in order to form a first cooling module. Furthermore, a second group of thermoelectric converters of the plurality of thermoelectric converters can be arranged on a second heat sink of the plurality of primary heat sinks in order to form a second cooling module. The first cooling module and the second cooling module can be arranged vertically or horizontally one after the other and/or adjacent to each other in the direction of flow of the heat transfer medium. Accordingly, the cooling capacity of the additional cooling device can be scaled by the number of cooling modules. The cooling modules can also be arranged at a distance from one another. Advantageously, each cooling module is arranged substantially completely in the flow of the heat transfer medium, so that each cooling module can effectively extract heat from the heat transfer medium.
The cooling modules can achieve a gradual cooling of the heat transfer medium, wherein the cooling modules can be controlled uniformly or individually. The cooling modules can have different cooling capacities. For example, the first cooling module, which is connected upstream of the second cooling module in the flow direction of the heat transfer medium, can have a higher cooling capacity or can be controlled accordingly in order to generate a higher cooling capacity. Here the relative performance specifications relate in each case to the downstream, second cooling module. The second cooling module can effect a further cooling of the heat transfer medium. Advantageously, the second cooling module is controlled in such a way that a smaller temperature difference is generated between the input and the output of the second cooling module, which difference can in particular be set with a higher accuracy. Accordingly, the first cooling module can form a coarse stage for setting the temperature of the heat transfer medium and the second cooling module can form a fine stage for setting the temperature of the heat transfer medium. Furthermore, the temperature setting of the heat transfer medium can be divided among a number of cooling modules. Alternatively, the cooling modules can be controlled identically in order to reduce the control outlay.
Depending on a specified cooling capacity, a specified number of thermoelectric converters per cooling module and/or a specified number of cooling modules can be provided. Advantageously, an optimum ratio of the surface area of the cold side of the respective thermoelectric converter, the cooling capacity of the respective thermoelectric converter, and the number of thermoelectric converters can be determined. Furthermore, the thermoelectric converters can be selected and arranged such that a base surface of the heat sink is covered as completely as possible.
The cooling modules can be arranged on the gas cooler, wherein at least one open side of the heat sinks is aligned in the direction of the gas cooler. It can thereby be achieved that the heat transfer medium can flow from the heat sink to the gas cooler. Furthermore, the cooling fins can be arranged in a flow direction of the heat transfer medium and perpendicular to an inflow surface of the gas cooler. The heat transfer medium can thus flow efficiently from the additional cooling device to the gas cooler.
The heat transfer medium chamber can be delimited by side walls of the first heat exchanger. Accordingly, the loss of cooled heat transfer medium can be reduced. The side walls can be formed at least partially by outer cooling fins of the heat sink. The side walls can limit a flow of the heat transfer medium laterally, in particular parallel to a flow direction of the heat transfer medium.
The first heat exchanger can be designed to enlarge the surface of the cold side in order to enlarge a coupling surface to the heat transfer medium. The surface area and/or mass of the cold side of a thermoelectric converter can be orders of magnitude smaller than the surface area, or mass, of the heat sink. When air is used as the heat transfer medium, the heat conduction from the cold side to the heat sink can also be higher than the heat conduction from the heat sink to the heat transfer medium. The heat sink can store the cooling capacity applied by the thermoelectric converter and transfer it to the heat transfer medium over a time interval that exceeds the active controlling of the thermoelectric converter.
The first heat exchanger can form an inlet opening into the heat transfer medium chamber, in particular the only inlet opening into the heat transfer medium chamber. It can thereby be achieved that the chamber can substantially be filled with cooled heat transfer medium. In particular, an exchange with the ambient atmosphere can be reduced. The inlet opening can be arranged on an upper side of the heat transfer medium chamber, so that cooled and correspondingly denser heat transfer medium remains within the heat transfer medium chamber. Accordingly, the transport device can operate in the direction of the natural convection of the cooled heat transfer medium. A first ventilator of the transport device can be arranged on the first heat exchanger, in particular on the inlet opening, and/or a second ventilator can be arranged on an inflow surface or an outflow surface of the gas cooler. The outflow surface of the gas cooler can be arranged on a side of the gas cooler facing away from the heat pump.
The transport device can be arranged on the first heat exchanger, preferably on a side surface of the first heat exchanger. The side surface can have a surface normal in the flow direction of the heat transfer medium. The transport device can have a plurality of ventilators which are arranged side by side on the side surface.
The first heat exchanger can have a plurality of cooling fins which are oriented in the direction of flow of the heat transfer medium. A flow resistance of the heat exchanger can thereby advantageously be reduced.
The transport device can be designed to generate a flow of the heat transfer medium substantially in the direction of the cooling fins. As a result, the heat transfer medium can flow along the side surfaces of the cooling fins and release heat to the side surfaces of the cooling fins. As a result, an efficient transport of the heat transfer medium from the first heat exchanger in the direction of the gas cooler can be realized. In particular, the transport device can draw in cooled heat transfer medium and conduct it in the direction of the gas cooler.
The additional cooling device can have a second heat exchanger. The second heat exchanger can be designed to improve a thermal coupling of the warm side and the secondary heat transfer medium. In particular, the second heat exchanger can deliver heat from the warm side to the secondary heat transfer medium and can effectively enlarge the surface of the warm side by a surface of the second heat exchanger. A contact surface of the warm side can thus be enlarged with the secondary heat transfer medium.
The second heat exchanger can be designed in the same way as the first heat exchanger. The warm side can be connected, in particular glued, to the second heat exchanger in order to realize an effective thermal coupling of the second heat exchanger to the warm side.
The second heat exchanger can be formed by a plurality of secondary heat sinks, and the first group of thermoelectric converters of the plurality of thermoelectric converters can be arranged with the corresponding warm side at a first heat sink of the plurality of secondary heat sinks. Furthermore, the second group of thermoelectric converters of the plurality of thermoelectric converters can be arranged with the corresponding warm side at a second heat sink of the plurality of secondary heat sinks, and the secondary heat sinks can be arranged one after the other and/or adjacent to one another in the flow direction of the secondary heat transfer medium. Accordingly, heat dissipation at the respective warm side can be realized as a mirror-inverted image of heat absorption at the respective cold side. As a result, the heat absorbed by the corresponding thermoelectric converters can efficiently be dissipated to the ambient air. The secondary heat sinks can emit heat to the ambient air by means of natural convection. Heated secondary heat transfer medium can be guided by the separating wall in such a way that it does not act directly on parts of the inlet flow of the heat transfer medium. The second heat exchanger can be designed to enlarge the surface of the warm side in order to increase the coupling surface to the secondary heat transfer medium.
The secondary transport device can be arranged on the second heat exchanger, in particular on a side surface of the second heat exchanger. A flow direction of the secondary heat transfer medium can thereby be determined. The flow direction can be directed in such a way that the heated secondary heat transfer medium does not flow in the direction of the heat transfer medium. For example, the flow direction of the secondary heat transfer medium and of the heat transfer medium can run parallel to the separating wall. Alternatively, the secondary heat transfer medium can be dissipated by the secondary transport device in the direction of a surface normal of the separating wall.
A plurality of secondary heat sinks can be arranged one after the other, forming a waste heat tunnel. The waste heat tunnel can be cuboid in shape and open or partially open at two or three sides. The heat sinks can be comb-shaped. The secondary transport device can be arranged on a side surface of a last heat sink of a plurality of secondary heat sinks. As a result, the secondary heat transfer medium can be sucked in both parallel to a base surface of the heat sink and perpendicular to the base surface of the heat sinks.
The secondary transport device can be arranged at a tunnel outlet, wherein the secondary transport device can be designed to suction the secondary heat transfer medium through the waste heat tunnel. An effective heat absorption from the secondary heat sink can be realized by this. The secondary transport device can be arranged at a tunnel entrance and designed to transport, in particular to blow, the secondary heat transfer medium through the waste heat tunnel.
The second heat exchanger can have a plurality of cooling fins which are aligned in the flow direction of the secondary heat transfer medium so that the second heat exchanger forms a reduced flow resistance for the secondary heat transfer medium.
The secondary transport device can be designed to generate a flow of the secondary heat transfer medium substantially in the direction of the cooling fins. As a result, the secondary heat transfer medium can flow along the side surfaces of the cooling fins and absorb heat at the side surfaces of the cooling fins.
The secondary transport device can be designed to generate a flow of the secondary heat transfer medium substantially perpendicular to a surface normal of the warm surface. Accordingly, the secondary heat transfer medium can flow along the warm surface, or the heat sink arranged at the warm surface, in order to absorb heat.
The flow direction of the heat transfer medium, in particular before it enters the gas cooler, can be oriented substantially parallel to the flow direction of the secondary heat transfer medium. Accordingly, a common air flow formed by the ambient atmosphere can be split into the heat transfer medium and the secondary heat transfer medium. Due to the parallel flow direction, the advantage can be realized that the transport device and the secondary transport device efficiently transport the relevant refrigerant. In particular, air flows influencing or canceling one another out can be prevented.
The additional cooling device can comprise a heat transfer medium which is arranged between the thermoelectric converter and the refrigeration circuit, in particular between the thermoelectric converter and the gas cooler. The heat transfer medium can increase the thermal conductivity of a contact surface between the additional cooling device and the gas cooler. The gas cooler and/or the first heat exchanger can be arranged in the heat transfer medium in order to realize a heat transfer from the gas cooler to the heat pump. The heat transfer medium can in particular be a liquid, for example water. The heat transfer medium can be a heat-conducting paste which improves surface contact between the additional cooling device and the refrigeration circuit, for example between the first heat exchanger and the gas cooler. A contact surface can be increased by compensating for unevenness.
The heat transfer medium can be designed to reduce the thermal resistance between the thermoelectric converter and the refrigeration circuit. The cooling efficiency of the additional cooling device can thereby be increased. In particular, the loss of refrigeration capacity to the environment can be reduced.
The cooling system can have a control device which is configured to operate the additional cooling device in such a way that the refrigerant in the gas cooler is in a subcritical state. In particular, the cooling capacity of the additional cooling device can be controlled depending on the ambient temperature.
The control device can be designed to detect at least one of the following system parameters: a temperature of the refrigerant before, after and/or in the gas cooler, a pressure of the refrigerant before, after and/or in the gas cooler, a temperature of the refrigerant between the compressor and the evaporator, a pressure of the refrigerant between the compressor and the evaporator, a temperature of the refrigerant between the evaporator and the expansion valve, a pressure of the refrigerant between the evaporator and the expansion valve, a temperature of the ambient atmosphere, a temperature of the heat transfer medium in the flow direction after the heat pump, a power consumption of the heat pump, a power consumption and/or delivery rate of the transport device, a power consumption and/or delivery rate of the secondary transport device. In particular, it can thereby be achieved that the refrigerant remains in a subcritical range during a cycle in the refrigeration circuit.
In general, the control device can control the additional cooling device in such a way that a predetermined degree of cooling is provided in order to achieve a desired cooling effect and/or a desired system performance. This can provide a simple and effective control arrangement for the cooling system.
The control device can be designed to control the power consumption of the heat pump. The heat transfer capacity of a thermoelectric converter can be proportional to the electrical power consumed. Accordingly, the temperature of the cold side and thus the cooling capacity of the thermoelectric converter can be controlled by adjusting the electrical power. A current- and/or voltage-limiting control can be used here.
The control device can be designed to control a cooling capacity of the heat pump, a refrigerant delivery capacity of the transport device, and/or a refrigerant delivery capacity of the secondary transport device, depending on at least one of the system parameters. Advantageously, a refrigerant delivery rate of the transport device can be controlled as a function of a cooling capacity of the heat pump in order to minimize losses of the generated cooling capacity to the environment.
The control device can be designed to regulate the performance of the compressor, in particular by adjusting the compressor rotational speed. The compressor speed can be used to control the compression capacity of the compressor. In particular, the compressor performance can be used to control the pressure of the refrigerant.
The control device can be designed to control the expansion valve in order to relax the refrigerant, i.e., reduce its pressure.
According to a further aspect, the invention also relates to a laboratory instrument which comprises the above-described cooling system. According to one embodiment, the laboratory instrument can be a centrifuge, wherein a rotor chamber can be cooled by the cooling system.
The laboratory instrument can be a standing instrument or a bench instrument. In particular, the laboratory instrument can be provided for use in closed spaces. The laboratory instrument can be coupled to a ventilation system for heat exchange. Furthermore, cooling of an exhaust air of the laboratory instrument can be realized by heat dissipation to the environment and/or by a periodic or continuous exchange or cooling of the ambient atmosphere. The performance of the cooling system can be scaled with its suitability as a bench instrument or free-standing instrument. In particular, compared to a bench instrument, a free-standing instrument can have an increased cooling capacity of the refrigeration circuit and thus also of the additional cooling device.
The laboratory instrument can comprise a housing. The cooling system can be arranged in the housing or at least partially in the housing. For example, the second heat exchanger can be arranged outside, preferably on the outside of the housing, in order to transfer heat directly to the ambient air, or to the secondary heat transfer medium. With an arrangement of the first heat exchanger inside the housing, the refrigeration capacity, or heat extraction, of the cooled heat transfer medium at the gas cooler can be increased. The separating wall can form a part of the housing. For example, the separating wall can form a rear side of the housing.
The second heat exchanger can be arranged on the rear wall. Accordingly, the second heat exchanger can be thermally insulated from an atmosphere within the instrument interior. A heat input of the secondary heat transfer medium into the heat transfer medium can be reduced by a flow of the secondary heat transfer medium away from an intake opening of the heat transfer medium.
The transport device can be designed to generate a flow of the heat transfer medium through the housing. As a result, further components, or the laboratory instrument as a whole, can be cooled. Accordingly, the additional cooling device can also contribute to cooling the centrifuge, specifically the rotor chamber.
The transport device can be designed to generate a flow of the heat transfer medium from the rear side of the instrument toward the front of the instrument, and/or the transport device can be designed to conduct the heat transfer medium through the gas cooler. Accordingly, the advantage can be achieved of increased heat absorption of components within the laboratory instrument. In addition, the heated heat transfer medium can flow out of the laboratory instrument as far away as possible from an intake opening for the heat transfer medium.
The housing can have a floor surface. The floor surface can form a base surface for fastening the components of the cooling system.
The separating wall can at least partially form the floor surface. As a result, the separating wall can be angled in order to form the heat transfer medium chamber. In addition, the additional cooling device can as a result be arranged at a distance from the gas cooler, so that a receiving space for the first heat exchanger is formed.
The separating wall can be connected, in particular screwed, to the floor surface. The advantage can thereby be achieved that a connection between the floor surface and the separating wall is as impermeable as possible to the heat transfer medium, in order to prevent cooling capacity losses due to an exiting of cooled heat transfer medium before it flows through the gas cooler.
The laboratory appliance can have an extraction ventilator which is arranged on the floor surface and is designed to transport the heat transfer medium out of the housing. A flow direction of the heat transfer medium can be oriented substantially parallel to the floor surface. The ventilator arranged on the floor surface can change a flow direction of the heat transfer medium in order to conduct the heat transfer medium through the floor surface.
The invention is also defined by the following numbered embodiments.
System embodiments are named below. These embodiments are abbreviated with the letter “S” followed by a number. Whenever reference is made below to “system embodiments,” these embodiments are intended.
S1. Cooling system (100), wherein the cooling system (100) has:
Laboratory instrument embodiments are mentioned below. These embodiments are abbreviated with the letter “L” followed by a number. Whenever reference is made below to “laboratory instrument embodiments,” these embodiments are intended.
L1. Laboratory instrument (300) having a cooling system according to any one of the preceding embodiments.
L2. Laboratory instrument according to the preceding embodiment, wherein the laboratory instrument is a centrifuge.
L3. Laboratory instrument according to any one of the preceding laboratory instrument embodiments, wherein the laboratory instrument is a bench unit or a standing device.
L4. Laboratory instrument according to any one of the preceding laboratory instrument embodiments, wherein the laboratory instrument is a housing.
L5. Laboratory instrument according to any one of the preceding laboratory instrument embodiments having the features of the embodiments S54 and L4, wherein the separating wall forms a part of the housing.
L6. Laboratory instrument according to any one of the preceding laboratory instrument embodiments with the features of embodiments S54 and L4, wherein the housing has a rear wall (303) and the separating wall at least partially forms the rear wall.
L7. Laboratory instrument according to any one of the preceding laboratory instrument embodiments with the features of embodiments S82 and L6, wherein the second heat exchanger is arranged on the rear wall.
L8. Laboratory instrument according to any one of the preceding laboratory instrument embodiments with the features of embodiments S34 and L4, wherein the transport device is designed to generate a flow of the heat transfer medium through the housing.
L9. Laboratory instrument according to any one of the preceding laboratory instrument embodiments with the features of embodiment L8, wherein the transport device is designed to generate a flow of the heat transfer medium from a rear side of the instrument in the direction of a front side of the instrument, and/or wherein the transport device is designed to conduct the heat transfer medium through the gas cooler.
L10. Laboratory instrument according to any one of the preceding laboratory instrument embodiments with the features of embodiment L5, wherein the housing has a floor surface (302).
L11. Laboratory instrument according to any one of the preceding laboratory instrument embodiments with the features of embodiment L10, wherein the separating wall at least partially forms the floor surface.
L12. Laboratory instrument according to any one of the preceding laboratory instrument embodiments with the features of embodiment L10 and S54, wherein the separating wall is connected, in particular screwed, to the floor surface.
L13. Laboratory instrument according to any one of the preceding laboratory instrument embodiments with the features of embodiment L10, comprising a suction ventilator which is arranged on the floor surface and is designed to transport the heat transfer medium out of the housing.
The present invention will now be described with reference to the accompanying drawings, which illustrate embodiments of the invention. These embodiments exemplify and do not limit the present invention.
It is noted that not all drawings bear all reference signs. Instead, in some of the drawings, some of the reference signs have been omitted for brevity and ease of presentation. Embodiments of the present invention are described below with reference to the accompanying drawings.
Embodiments of the present invention enable the efficient use of a refrigerant in a laboratory instrument 300. In particular, a refrigerant with a critical temperature below a permissible ambient or operating temperature of a laboratory instrument 300 can be used in a subcritical range. This can be achieved by active cooling of a gas cooler 103 to keep the refrigerant below the critical point regardless of the ambient conditions.
The laboratory instrument 300 is preferably a centrifuge which can be cooled in particular by means of a compressor-based refrigeration circuit. Carbon dioxide (CO2, R744) can be used as the refrigerant. Embodiments of the invention are in particular directed to a cooling system 100, which can for example be part of the laboratory instrument. The cooling system 100 has a refrigeration circuit; see for example
The flow of the heat transfer medium can in particular be controlled by a transport device 205, for example a ventilator. The heat transfer medium is suctioned through the gas cooler 103 by means of the transport device 205. In this case, the flow direction is directed in particular into the interior of a housing of the laboratory instrument 300. As a result, the heat transfer medium can also at least partially flow around the other components 101, 102, 104 of the refrigeration circuit. The gas cooler 103 can be arranged on one side and/or on a base plate of the housing. Furthermore, an outer side 109 of the gas cooler 103 may delimit an inner space 301 of the laboratory instrument 300. The transport device 205 can be arranged on an inner side 110 opposite the outer side 109.
The cooling capacity of the gas cooler 103 can be dependent on the temperature of the heat transfer medium. For example, the gas cooler 103 can be designed to achieve a ΔT of XK between the temperature T1 of the refrigerant and the temperature T2 of the heat transfer medium. Typically, a gas cooler 103 can achieve a ΔT in the range of from 1 K to 5 K. Accordingly, T1 can always be greater than T2. As the ambient temperature rises, the refrigerant can reach/exceed the critical point even when cooled by the gas cooler 103. For example, the laboratory instrument 300 can be designed for an ambient temperature of, preferably, up to 40° C. Here, the critical point of CO2 as a refrigerant can be exceeded with cooling by the ambient air.
The refrigeration circuit then operates in an at least temporarily transcritical range. An exemplary enthalpy-pressure diagram for a transcritical cycle 113 is shown in
The transcritical vapor compression cycle for carbon dioxide includes compression of the vapor by the compressor so that a pressure, a temperature and an enthalpy are increased (right area of the square in
With CO2 as a refrigerant, the heat transfer can take place exclusively in the transcritical state without a phase transition. Accordingly, a heat exchange can be realized in the gas cooler 103 from the gaseous refrigerant to the gaseous heat transfer medium.
By cooling the heat transfer medium, a refrigeration capacity at the gas cooler 103 can be increased. In particular, at least one thermoelectric converter 202 can be used to cool the heat transfer medium (see for example
An exemplary calculated energy advantage of a subcritical cycle 114 compared to a transcritical cycle 113 is shown in
The energy saving can be described by a decreasing polytropic exponent at the transition from a transcritical process to a subcritical process. A compression line can become steeper and approach the isentrope. This can be due to an improved delivery rate and a lower pressure ratio.
The regions 119-1, 119-2 indicate an increased cooling capacity, which can be achieved by cooling using the thermoelectric converter. Furthermore, the region 120 indicates a reduced drive power of the compressor 102.
Typically, the gas cooler 103 (see again for example
The connection between the gas cooler outlet temperature and the criticality of the process results from the optimum high pressure. The optimal high pressure is typically pHopt=|2,44*tGaus[° C.]+1|*(bar), where tGaus is the gas cooler outlet temperature. Accordingly, the optimum high pressure can be decisively determined by the gas cooler outlet temperature. The use of CO2 results in an advantageous gas cooler outlet temperature of below 30° C., so that the optimum high pressure can be set to be subcritical.
Cooling down the heat transfer medium can reduce a performance disadvantage of a transcritical, single-stage CO2 refrigeration circuit. The increased pressure in transcritical operation can result from the increased gas cooler outlet temperature. Accordingly, the gas cooler outlet temperature can be lowered by cooling the heat transfer medium, so that the optimum high pressure can also be reduced. In the example shown, the optimum high pressure can be reduced from 98.8 bar to 69.5 bar.
Accordingly, a transcritical cycle 113 can be changed to a subcritical cycle 114 of the refrigeration circuit when the heat transfer medium is cooled. In this way, for example, a better heat transfer and a low drive power of the compressor 102 can be realized.
The drive power can in particular be dependent on the pressure of the refrigerant. By lowering the optimal pressure, the drive power and thus the power consumption can also be reduced accordingly. By reducing the pressure by preventing a transition of the refrigerant into a critical range, the components of the refrigeration circuit can be designed more simply, as a specification for low maximum pressures may be sufficient. By reducing the drive power, it is also advantageously possible to use less powerful compressors and/or compressor drive modules. Advantageously, a reduction in the drive power in comparison to transcritical cycles can be in the range from 10% to 50%, preferably in the range from 35% to 45%.
The gas cooler 103 can the primary agent for cooling the CO2, and thermoelectric converters 202 can be used to always cool the gas cooler 103. Cooled air can be supplied to the gas cooler 103 by means of a ventilator 205, and waste heat from the thermoelectric converters 202 can be dissipated by means of a further ventilator 206. Advantageously, the air flow on the cold side 203 is separate from the air flow on the warm side 204.
The refrigeration circuit can also have a multi-stage design (see
The laboratory instrument 300 can be a centrifuge, wherein the evaporator 101 can be arranged circumferentially on a rotor vessel in order to cool samples arranged in the centrifuge.
Preferably, the cooling system 100 has a control device 112 (see
Furthermore, a power of the thermoelectric converter 202 can be controlled in order to regulate a temperature of the heat transfer medium. Advantageously, a conveying capacity of the transport device 205, 206 can also be adjusted in order to control the flow of the corresponding heat transfer media.
The performance of the thermoelectric converters 202 can be controlled using a type-specific characteristic curve of the thermoelectric converters (see
For example, a group of thermoelectric converters 202 can be coupled in series with a heat sink. Preferably, 5-10 identical thermoelectric converters can be coupled with a heat sink at the respective cold sides. Each of the thermoelectric converters can achieve a refrigeration capacity of 60 W at a temperature of 25° C. In order to cool the heat transfer medium, a cooling capacity in the range of 500 W to 1000 W may be required. The cooling capacity can be scaled via the number of thermoelectric converters used. A single-row coupling of thermoelectric converters to a heat sink can be a minimum configuration with regard to the cooling capacity of the additional cooling device (see
The additional cooling device 108 can be arranged on the line system 104 of the refrigeration circuit or on a gas cooling line 106 of the gas cooler 103 (see
The heat sinks can have a thermal resistance Rth in a range from 0.055 K/W to 40 K/W, preferably 0.08 K/W or 0.19 K/W. The thermal resistance Rth can depend on the length of the heat sink. For a length of 100 mm in the vertical direction, the heat sink can have an Rth of 0.19 K/W. For an installed length of 400 mm, the Rth can be 0.08 K/W.
In one embodiment, a power in the range of 500 W to 1000 W can be transmitted. Correspondingly, the temperature difference can be 95 K for the shortest length of the heat sink of 100 mm. A thermoelectric converter that corresponds to a power characteristic shown in
In one embodiment, a second row of heat sinks, and correspondingly a second row of Peltier elements, can be provided. It can thus be achieved that a required power per Peltier element can be reduced to 30 W, and the possible temperature difference can rise to 45 K (see marking 402,
According to this embodiment, Peltier elements can be used which provide at least 30 watts at a temperature difference of 45 K. Other combinations of heat sinks and Peltier elements are possible if a corresponding cooling capacity can be provided.
Whenever a relative term such as “approximately,” “substantially,” or “about” is used in this document, that term is intended to include the exact term as well. That is to say, e.g., “substantially straight” should be construed to also include “(exactly) straight.”
Whenever steps are mentioned in this document, it should be noted that the order in which the steps are mentioned in this text may be random. That is, the order in which the steps are presented may be random unless otherwise specified or obvious to a person skilled in the art. That is, if in the present document, for example, it is stated that a method comprises steps (A) and (B), this does not necessarily mean that step (A) occurs before step (B), but it is also possible that step (A) (at least in part) is carried out simultaneously with step (B) or that step (B) occurs before step (A). Furthermore, if it is stated that a step (X) precedes another step (Z), this does not mean that there is no step between steps (X) and (Z). That is, step (X) before step (Z) comprises the situation that step (X) is performed directly before step (Z), but also the situation that (X) is performed before one or more steps (Y1), . . . , followed by step (Z). Corresponding considerations apply when terms such as “after” or “before” are used.
While a preferred embodiment has been described above with reference to the drawings, a person skilled in the art will understand that this embodiment has been provided for illustrative purposes only and should in no way be construed as limiting the scope of the present invention which is defined by the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2021 126 963.6 | Oct 2021 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2022/078688 | 10/14/2022 | WO |
