Patent Application
20060053821
This invention relates to a heat pump that is operable in both a cooling and a heating mode, and wherein a reheat coil is incorporated into the circuit.
Refrigerant systems are utilized to control the temperature and humidity of air in various indoor environments to be conditioned. In a typical refrigerant system operating in the cooling mode, a refrigerant is compressed in a compressor and delivered to a condenser (or outdoor heat exchanger in this case). In the condenser, heat is exchanged between outside ambient air and the refrigerant. From the condenser, the refrigerant passes to an expansion device, at which the refrigerant is expanded to a lower pressure and temperature, and then to an evaporator (or indoor heat exchanger). In the evaporator heat is exchanged between the refrigerant and the indoor air, to condition the indoor air. When the refrigerant system is operating, the evaporator cools the air that is being supplied to the indoor environment. In addition, as the temperature of the indoor air is lowered, moisture usually is also taken out of the air. In this manner, the humidity level of the indoor air can also be controlled.
The above description is of a refrigerant system being utilized in a cooling mode of operation. In the heating mode, the refrigerant flow through the system is essentially reversed. The indoor heat exchanger becomes the condenser and releases heat into the environment to be conditioned (heated in this case) and the outdoor heat exchanger serves the purpose of the evaporator and exchangers heat with a relatively cold outdoor air. Heat pumps are known as the systems that can reverse the refrigerant flow through the refrigerant cycle in order to operate in both heating and cooling modes. This is usually achieved by incorporating a four-way reversing valve or an equivalent device into the system schematic downstream of the compressor discharge port. The four-way reversing valve selectively directs the refrigerant flow through indoor or outdoor heat exchanger when the system is in the heating or cooling mode of operation respectively. Furthermore, if the expansion device cannot handle the reversed flow, than a pair of expansion devices, each along with a check valve, are to be employed instead.
In some cases, while the system is operating in the cooling mode, the temperature level, to which the air is brought to provide a comfort environment in a conditioned space, may need to be higher than the temperature that would provide the ideal humidity level. This has presented design challenges to refrigerant system designers. One way to address such challenges is to utilize various schematics incorporating reheat coils. In many cases, the reheat coils, placed on the way of indoor air stream behind the evaporator, are employed for the purpose of reheating the air supplied to the conditioned space after it has been cooled in the evaporator, and where the moisture has been removed.
While reheat coils have been incorporated into the air conditioning systems operating in the cooling mode, they have not been incorporated into heat pumps that are operable in both cooling and heating modes. Thus, a reheat coil would provide an enhanced control over temperature and humidity in heat pump applications as well.
In a disclosed embodiment of this invention, a refrigerant heat pump system is operable in either a cooling or a heating mode by reversing the flow of refrigerant from the compressor through the circuit by utilizing a main flow control device such as a four-way reversing valve. A reheat coil is incorporated into the circuit, and is selectively operated in the cooling mode to receive a flow of a relatively hot refrigerant, and reheat an airflow (by means of heat transfer interaction with this refrigerant) to a higher temperature than would otherwise be provided by the conventional design schematic. In general, the reheat coil allows for the dehumidified air to be supplied to an environment to be conditioned at the desired temperature. A stream of air is passed over an indoor heat exchanger, which will maintain the air at a low temperature, assuring enough moisture to be removed from the air, but at the same time at a temperature lower than desired in the conditioned environment. At least a portion of this air is then passed over the reheat coil, where it is reheated to the target temperature.
While preferred schematics are disclosed, design variations would come within the scope of this invention.
The following specification and drawings are not intended to cover a wide variety of the known reheat circuit designs and only show exemplary circuit schematics to convey the benefits obtained from the teachings of this invention.
In the heating mode, the refrigerant passes from the discharge line 14, through the four-way valve 18, to the indoor heat exchanger 24, the expansion device 22, the outdoor heat exchanger 20, once again to the four-way valve 18, to the suction line 16, and finally back to the compressor 12. In the heating mode, the air flowing over the indoor coil 24 (a condenser in this case) is heated before entering the conditioned space.
As known in the art, in case the expansion device 22 cannot handle the reversed flow, it has to be substituted by two assemblies, each containing a unidirectional expansion device and a check valve for control of refrigerant flow in the appropriate direction.
As shown in
The reheat coil is positioned to be in the path of air passing over the indoor heat exchanger 24. The reheat coil is utilized in the cooling mode of operation when a system control determines it would be desirable to predominantly have dehumidification of the air being supplied to an environment to be conditioned, while maintaining the temperature level. The system control manages the refrigerant flow and system operation such that the indoor heat exchanger 24 conditions the airflow heading to the indoor environment to be cooled and dehumidified with at least a portion of that air then being passed over the reheat coil, which reheats the air to the desired temperature for the environment. Thus, by utilizing reheat coil 32 in the cooling mode, the present invention provides better control over the operation of a heat pump in terms of temperature and humidity, enhancing its operational flexibility and establishing a broader coverage of the external latent and sensible load demands. Although a hot gas reheat schematic is shown in
The embodiment 40 illustrated in
It has to be understood that all flow control devices can be either of the conventional shutoff or regulating type, with the latter option infinitely increasing system flexibility. Furthermore, a single three-way valve can replace a pair of the conventional valves 41 and 44 to perform identical bypass functionality of obtaining a variable sensible heat ratio. A worker ordinarily skilled in the art can design an appropriate control.
While particular schematics for the reheat circuits are disclosed, it is well understood by a person ordinarily skilled in the art that many other reheat circuit designs could be utilized and will provide the full benefits obtained from the teachings of the invention. Thus, the present invention broadly extends to the integration of a reheat circuit into a heat pump system that is operable in both heating and cooling modes and provides advantages of control flexibility over temperature and humidity in order to satisfy sensible and latent load demands.
Although preferred embodiments of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
