Patent Application
20060080988
The present invention relates to a gas cooler and chassis for a transcritical heat pump water heater.
One type of transcritical heat pump water heater uses a heat pump cycle that utilizes CO2 as the working fluid. The heat pump may be located indoors or on the exterior of a building, for example, mounted on a roof top of a building. Numerous components are located within a chassis that supports the components, which includes for example a compressor, a gas cooler, an expansion device, an evaporator, an accumulator, and other various components.
In a CO2 heat pump water heating system, super critical CO2 rejects heat in the gas cooler to water, and sub-critical CO2 absorbs heat in the evaporator from the outdoor air. The heat pump system must operate desirably under a wide range of conditions. For example, the outdoor air temperature may vary from −10° F. in the winter to the 120° F. in the summer. A draft fan is usually used to force the airflow through the evaporator fin side to supply heat to the refrigerant flowing in the tube side of the evaporator. Insuring the maximum possible flow through the evaporator enables the heat pump to operate desirably throughout various airflow conditions.
Previously, the gas cooler was designed only to efficiently achieve its function without consideration to the gas cooler's impact on the efficiency of other components. The gas cooler is often packaged as a rather large box-like component having insulation around the interior fluid passages to reduce heat loss. The box extends a significant distance into the cavity defined by the chassis, which also houses the various heat pump components. As a result, the gas cooler blocks and significantly inhibits the air flow through the chassis compromising the efficiency of the heat pump evaporator and ability of the evaporator to perform desirably under the various operating conditions. Therefore, what is needed is an improved gas cooler and chassis arrangement that minimizes the negative impact of the gas cooler on the evaporator as well as system performance, i.e. minimizing airflow blockage.
The present invention relates to a gas cooler and chassis integration design suitable for a transcritical heat pump water heater. The heat pump system includes a chassis for supporting such system components as a gas cooler and evaporator. The gas cooler includes a water supply and return opening and a refrigerant inlet and outlet opening with associated passages running through the gas cooler. The water and refrigerant passages are positioned in relationship to one another such that heat from the compressed refrigerant is transferred to the water flowing through the water passage to provide heated water to a water tank.
The dimensions of the gas cooler are designed to minimize the impact that the gas cooler has on the cooling capacity of the evaporator by reducing the amount of air flow that the gas cooler blocks. This is achieved by optimizing the way to package the gas cooler, for example, by reducing the depth that the gas cooler extends into the chassis cavity. As a result, the height and/or width of the gas cooler is increased compared to other similar volume gas coolers while still providing comparable water heating capacity. As a result, a shorter length of the evaporator coils is affected by the blocked airflow.
A typical heat pump chassis includes spaced apart vertical and horizontal walls supported by the vertical and horizontal supports that define the dimension of the chassis. The walls and supports generally define an outer shape. The chassis provides not only support to the components of the heat pump water heater but also forms the access interface for operation and maintenance purpose. Various components of the heat pump are arranged and interconnected inside the chassis to form a closed refrigerant loop. In one example, a face of the gas cooler is located adjacent to a substantial portion of the wall, for example, greater than 50 percent.
In an example shown, four sides of the gas cooler are located proximate to the spaced apart horizontal and vertical supports providing a gas cooler having a thin profile that does not extend very deeply into the chassis cavity. Additionally, the gas cooler may provide one of the exterior sides of the chassis, eliminating a separate wall used in the prior art. Preferably, the depth of the gas cooler is less than the width and/or the height. Also, the chassis may incorporate one or more guides so that the thin-profiled inventive gas cooler may be removably received within a portion of the housing preferably proximate to an outer wall of the chassis.
Accordingly, the present invention provides an improved gas cooler and chassis arrangement that minimizes the negative impact the gas cooler has on the evaporator and system performance by blocking the airflow to the evaporator.
Other advantages of the present invention can be understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
As can be seen in
The refrigerant exits the compressor 122 at a high pressure and a high enthalpy. The refrigerant then flows through the gas cooler 124 at a high pressure. A fluid medium 130, such as water or air, flows through a heat sink 132 of the gas cooler 124 and exchanges heat with the refrigerant flowing through the gas cooler 124. In the gas cooler 124, the refrigerant rejects heat into the fluid medium 130, and the refrigerant exits the gas cooler 124 at a low enthalpy and a high pressure. A water pump 134 pumps the fluid medium through the heat sink 132. The cooled fluid medium 130 enters the heat sink 132 at the heat sink inlet or return 136 and flows in a direction opposite to the direction of the flow of the refrigerant. After exchanging heat with the refrigerant, the heated water 138 exits the heat sink 130 at the heat sink outlet or supply 140. The heated water can be stored in a water tank 164. In one example, the water tank 164 is sized to meet expected peak demand at all times. The refrigerant then passes through the expansion valve 126, which expands and reduces the pressure of the refrigerant. The expansion device 126 can be an electronic expansion valve or other known type of expansion device.
After expansion, the refrigerant flows through the passages 180 of the evaporator 128 and exits at a high enthalpy and a low pressure. In the evaporator 128, the refrigerant absorbs heat from the outdoor air 144, heating the refrigerant. The outdoor air 144 flows through a heat sink 146 and exchanges heat with the refrigerant passing through the evaporator 128 in a known manner. The outdoor air 144 enters the heat sink 146 through the heat sink inlet or return 148 and flows in a direction opposite to or cross to the direction of flow of the refrigerant. After exchanging heat with the refrigerant, the cooled outdoor air 150 exits the heat sink 146 through the heat sink outlet or supply 152. The temperature difference between the outdoor air 144 and the refrigerant in the evaporator 128 drives the thermal energy transfer from the outdoor air 144 to the refrigerant as the refrigerant flows through the evaporator 128. A fan 154 moves the outdoor air 144 across the evaporator 128, maintaining the temperature difference and evaporating the refrigerant. The refrigerant then reenters the compressor 122, completing the cycle.
The system 120 transfers heat from the low temperature energy reservoir (ambient air) to the high temperature energy sink (heated hot water). The transfer of energy is also achieved with the aid of electrical energy input at the compressor 122, fan 154 and pump 134.
The system 120 can also include an accumulator 156. The accumulator 156 stores excess refrigerant from the system 120 to control the high pressure of the system 120, and therefore the coefficient of performance.
Referring to
Furthermore, as depicted in
The inventive features of the gas cooler 24 and its relationship relative to the chassis 12 may be expressed in any number of ways. Referring to
In one example, the area A2 is at least 50 percent of the area A1. In the example shown in
Referring to another feature of
It should also be understood that the removable gas cooler configuration shown in
The inventive gas cooler 24 reduces the blockage of air to the evaporator coil so that the negative impact on the evaporator and subsequently the water heat performance is minimized. In addition, the configuration of the gas cooler 24 within the chassis 12 provides user access to the components within the chassis, in particular, the arrangement shown in
The invention has been described in an illustrative manner, and it is to be understood that the terminology that has been used is intended to be in the nature of words of description rather than of limitation. Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
