Patent Application
20100024440
The present invention relates to the removal of heat from an environment by the flow control of cryogenic elements through a heat exchanger, thus controlling the enthalpic potential of said cryogenic elements.
Due to an increasing demand for technology that is both electrically efficient and environmentally responsible, there exists a need to develop technologies that address the cooling of environments such as Data Centers or other IT operations, thermal stress test chamber, or a Logistical Delivery Transport truck. In refrigerated trucks or trailers which commonly transport sensitive food products, refrigeration failure can be costly in terms of food spoilage and business disruption. Excursions in temperature or outright failure may be catastrophic in the biomedical field. For example, the destruction of a limited supply of special vaccine, stored under very low temperature for emergency protection of the general public, is highly undesirable.
Similarly, in the telecommunications, information storage and exchange industries i.e. Data Centers, there is an increasing need for reliable cooling of racks of servers in these environments. A failure of the cooling equipment can lead to failures in the servers, which can mean downtime for mission critical software and hardware failure for customer web application software. In the electronics stress testing field, reliable environmental simulation chambers need to achieve very low temperatures to properly test their loads/products. Additionally, back up cooling systems may be needed to supplement existing conventional cooling systems. These chambers may need to support a temperature range from room temperature (25 degrees C.) down to a cryogenic temperature as low as −150 degrees C.
Given all of these technological requirements and specifications, there has been the introduction of the requirement to be environmentally responsible with the use of electrical power and to reduce the carbon footprint of these operations. This need to reduce electrical power consumption in the controlling of heat in an environment and replace that consumption with a renewable resource has given way to the embodied concept of flow control of a cryogenic element for removing heat.
In one aspect, a system the provides the flow control of a cryogenic element to remove heat from an environment that includes a cryogenic storage to store a cryogen; a cryogenic delivery system coupled to the cryogenic storage to transport the cryogen; a distributor coupled to the cryogenic delivery system, the distributor having a plurality of distribution lead tubes to evenly distribute the enthalpic potential of the cryogenic element; and a heat exchanger coupled to the distribution lead tubes.
Implementations of the above aspect may include one or more of the following. Fluid or air can be used as the temperature heat exchange medium. The cryogenics delivery system can be vacuum insulated (VIP) supply hoses and valves. The system can use a VIP proportional control valve set up with a redundant safety valve that closes in a fail position without requiring power. The cryogenic air heat exchanger can include one or more circuits in the air coil and can have one or more redundant air coil circuits. The cryogen is distributed evenly throughout a heat exchanger. The cryogenic delivery system can have one or more relief valves. The distributor can have a pressure drop zone to facilitate enthalpic processes. The distributor can have an outlet at one end to distribute the cryogenic element. The outlet can be cone-shaped and can include a cone inside to equalize the pressure and flow of the cryogenic element. The distributor can have one or more nozzles. A coil plate fin can be used to receive one or more coil circuits, where each coil circuit can have a coil tube. The coil plate can be a plate fin heat exchanger such as aluminum or copper, or other heat exchanger types such as a plate heat exchanger, regenerative or modified economizer heat exchanger. A reliquifier can be used at the end to reuse the cryogen. Alternatively, an exhaust capture unit can be used to recycle gas exhaust to an alternate recovery process. The cryogenic delivery system can have one or more proportional proportional-integral-derivative (PID) control valves. The distributor can have an orifice. The orifice is sized to deliver the cryogenic element with the appropriate enthalpy for the application and apply the element to the heat exchanger. The heat exchanger can have one or more cryogenic coils, where the size of the cryogenic coil is determined by the air flow needed to move air through a predetermined volume. A fan can generate air flow, wherein the size of the fan is determined based on a predetermined volume. One or more control sensors placed at an inlet and an outlet of a heat exchanger to measure an average temperature, and the output can be used by a PID controller to accurately provide control of the cryogenic element for appropriate heat transfer.
In another aspect, a system provides the flow control of a cryogenic element to remove heat from an environment. The system includes a cryogenic storage to store a cryogen; a cryogenic delivery system coupled to the cryogenic storage to transport the cryogen; a distributor coupled to the cryogenic delivery system, the distributor having a plurality of distribution lead tubes to evenly distribute the enthalpic potential of the cryogenic element; a heat exchanger coupled to the distribution lead tubes; and a controller to provide a flow control of the cryogenic element to remove heat from the environment in a closed-loop.
In another aspect, systems and methods are disclosed to provide a cryogenic air cooling system with air flow as the heat transfer medium. The system can be closed loop to avoid discharging the cryogenic elements into the controlled space.
Advantages of preferred embodiment may include one or more of the following. The system can achieve a target temperature of, or within the ranges of, +20, 0, −10 −20, −40, −60, −80, −120, −150, deg. C. and can continuously maintain that temperature accurately and reliably. The preferred embodiment provides temperature accuracy independent of ambient conditions of temperature and humidity while maintaining electrical efficiency and environmentally responsible operation through the use of a renewable resource heat exchange methodology.
The system provides cryogenic heat exchange of air using cryogenic elements. The temperature range is from +25 degrees Centigrade to −150 degrees Centigrade. The low temperature prevents raw material biodeterioration when biological materials are stored.
The system can also be used for refrigerated logistical delivery transport trailers, thermal stress testing chambers, data center rooms and Computer/IT controlled environments. Operating cost for the preferred embodiment can be lowered due to a reduction in electrical power needed to operate the conventional systems. The operating costs are lowered by the combination of the cryogenic air conditioning or refrigeration process and the use of an efficient delivery system that may include vacuum insulated piping materials.
The supply line 106 can be a vacuum insulated piping (VIP) line to minimize the vaporization of the cryogens during the transfer of the cryogenic liquids due to heat gain and vaporization. With vacuum insulated piping, the vacuum insulation decreases heat gain caused from conduction, convection, or radiation. In one embodiment, a multi-layer insulation is demonstrably superior to conventional foam insulated copper piping in reducing heat gain to the transferred cryogenic flow.
Fittings for input and output connection to the air heat exchanger air conditioning and or refrigeration source are configured and welded or bayoneted with cryogenic connectors in place. Preferably, the connection between the vacuum insulated pipes is done with a bayonet connector that uses thermal contraction/expansion mechanisms. The contraction/expansion provides a mechanical connection for sections of vacuum insulated pipe with a low heat gain connection. The bayonets are constructed of stainless steel with the nose piece of the male bayonet being made from a dissimilar material such as the polymer INVAR36 to prevent mechanical seizing. A secondary o-ring seal is used at the flange of each bayonet half to provide a seal in which a gas trap is formed between the close tolerance fitting sections of the bayonet assembly. This gas trap is formed using the initial cryogen flow which is vaporized and forms a high pressure impedance for the lower pressure liquid, thus forming a frost free connection with lowered heat gain to the cryogenic flow.
A manual shut-off valve 108 is connected to the supply line 106 to allow a user to shut-off the system in case of an emergency. The LN2 liquid passes through a redundant valve 110 and enters another valved supply line 112. The supply line 112 has a relief valve 114 and is gated by a control valve 116. In one embodiment, a VIP control valve set up is provided with a redundant safety valve. The safety valve is of the EMO (emergency machine off) type, closed with power removed. The LN2 liquid then travels through a distributor 118 which evenly controls the flow of the cryogenic element over a plurality of lead tubes 120. The lead tubes 120 then complete the enthalpy control to a heat exchanger/evaporator 130 such as the Multi Tube Hi Reliability Tubing discussed in U.S. Pat. No. 6,804,976, the content of which is incorporated by reference.
The lead tubes 120 exit the heat exchanger 130 at a distributed outlet 132. A portion of the Gasses can be vented to the outside through a vent line 134, and the majority is recirculated and reused through a reuse outlet 136. The cryogenic system can be tied to a reliquifier and the cryogenic elements can be reprocessed. Alternatively, the exhaust from the gas exhaust can be used for a different process as Controlled atmosphere to reduce Bio-Deterioration within the payload bay or chamber within the heat source environment.
Preferably, the distribution of the cryogenic element is constant in flow and pressure though out the air coil and/or refrigerant heat exchanger coil or high reliability multi-tube thermal exchange structure as disclosed in U.S. Pat. No. 6,804,976 (the content of which is incorporated by reference), thus maintaining the enthalpy, kinetic potential, of the cryogenic element and the heat exchanger. The manipulation of the various parts of the system, thus controlling the enthalpy, is accomplished using the feedback control described within. The control of the cryogenic element via the comparative function of temperature of the heat exchanger and incoming load constitutes the flow control of a cryogenic element for removing heat. Changing any/all of the various parts of the system, either in real time or via manufacturing change, denotes a recalculation of the enthalpy of the system, thus adjusting for constant change in source heat load or application changes from site to site.
The lead tube 220 is connected to a coil tube 238 which supports a coil circuit 242 to maximally expose the coil tube 238 to the heat source annotated as arrows 248. Preferably, the cryogenic heat exchanger has one or more circuits 242 in the air coil 238 including redundant circuits. The redundant circuits allow reliable operation in case the other circuit(s) fails.
In one embodiment, the tubing fittings for input and output connection to air heat exchanger coil tube 238 are configured and welded or bayoneted with cryogenic connectors in place.
The use of a heat exchanger results in the relatively rapid warming and vaporization of the cryogenic elements. While in transit in coil tube 238, heat from the heat source 248 warms the coil tube 238 thus allowing for the transfer of energy from the heat source to the cryogenic element. Generally, the heat exchanger takes the form of heat transfer elements or sleeves which surround and closely contact the coil tubes 238 through which the cryogenic fluid is passing. These sleeves are made from a material having a relatively high thermal conductivity and typically are provided with fins or other extended surfaces in order to increase their surface area, thereby resulting in even distribution of the enthropic processes. The heat exchanger units consist of a plurality of separate sleeve sections which are arranged in a vertical parallel fashion and which are interconnected by a manifold system so that the cryogenic element passes through them in a serpentine fashion.
In one embodiment, the heat transfer sections have long, multi-finned extruded aluminum or copper sections. The heat exchangers can be plate-fin type heat exchangers. As the cryogenic element is passed through the plate fin, heat is transferred from the heat source to the cryogenic element. A vaporizer unit can have a plurality of such heat transfer sections disposed vertically and arranged in a bank. The sections were connected in series, with the output opening of one section being welded to the input opening of the next section.
The aluminum or copper cold plates and plate-fin heat exchangers are lightweight and yet provide high performance.
Next, the control valve is selected (1006). The control valve needs to be of the proportional control type incorporating a control component with proportional-integral-derivative (PID) functions and temperature comparative functions. (Next, the size of the heat exchanger coil is determined as a function of the heat source/enthalpy ratio. (1008).
After the coil size is determined the size of the fan system is calculated (1010). After the components have been defined, the system's total size and foot print can be determined (1012).
The flow control of the cryogenic element is performed as a function of temperature at the heat exchanger can use a PID controller for accurate temperature control. For the PID controller, control sensors are placed at the inlet and the outlet of the heat exchanger to collect an average temperature for proper application of the enthalpic potential of the cryogenic element (1014).
The temperature range is from ambient e.g +75 degrees Fahrenheit to −120 degrees Fahrenheit. This system controls the flow of a cryogenic element which in turn controls the enthalpic potential of said cryogenic element as it is applied to a heat source which can be Refrigerated Trailers, Environmental Chambers, and computer cooling rooms, among others.
Although the invention has been described in detail in the foregoing for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art without departing from the spirit and scope of the invention except as it may be limited by the claims.
