HVAC system with multiple compressors and heat exchangers

A vapor compression system that includes a baffle that separates a first condenser and a first fan from a second condenser and a second fan. A controller that switches between first and second modes of operation. In the first mode of operation the controller closes a valve to block a flow of a refrigerant through a first condenser and turns off the first fan. In the second mode of operation the controller opens the valve to enable the flow of the refrigerant through the first condenser and turns on the first fan.

BACKGROUND

The invention relates generally to HVAC systems.

Heating, ventilation, and air conditioning (HVAC) systems condition enclosed spaces by exchanging energy between a refrigerant and air. HVAC systems accomplish condition air supplied to the enclosed spaces by circulating a refrigerant between two heat exchangers commonly referred to as an evaporator coil and a condenser coil. As refrigerant passes through the evaporator coil and the condenser coil, the refrigerant either absorbs or discharges thermal energy from an air stream or other fluid. More specifically, as air passes over the evaporator coil, the air cools as it loses energy to the refrigerant passing through the evaporator coil. In contrast, the condenser coil enables the refrigerant to discharge heat into the atmosphere as air flows over the condenser coil.

SUMMARY

The present disclosure relates to a vapor compression system that includes a baffle that separates a first condenser and a first fan from a second condenser and a second fan. A controller that switches between first and second modes of operation. In the first mode of operation the controller closes a valve to block a flow of a refrigerant through a first condenser and turns off the first fan. In the second mode of operation the controller opens the valve to enable the flow of the refrigerant through the first condenser and turns on the first fan.

The present disclosure also relates to a vapor compression system that includes a first valve that controls a flow of a refrigerant through a first condenser. A second valve that controls the flow of the refrigerant through a second condenser. A controller that closes the first valve and opens the second valve in a first mode of operation and closes the second valve and opens the first valve in a second mode of operation.

The present disclosure also relates to a vapor compression system that includes a first fan that moves a first fluid across a first condenser and a second fan that moves a second fluid across a second condenser. A baffle disposed between the first condenser and the second condenser and between the first fan and the second fan. The baffle reduces and/or blocks mixing of the first and second fluids. A controller that switches between first and second modes of operation. In the first mode of operation the controller turns off the first fan, and in the second mode of operation the controller turns on the first fan.

DETAILED DESCRIPTION

The integrated energy efficiency ratio (IEER) is a number that represents an HVAC system's part load performance, which enables energy comparisons among similar HVAC systems. The integrated energy efficiency ratio is calculated by summing weighted energy efficiency ratios (EERs) of the HVAC system at four different operating conditions. The four different operating conditions are commonly referred to as the A, B, C, and D points. In general, the A point EER measures the energy efficiency ratio of the HVAC system operating at 100% capacity in ambient conditions of 95° F. The B point EER measures the energy efficiency ratio of the HVAC system operating at 75% capacity in ambient conditions of 81.5° F. The C point EER measures the energy efficiency ratio of the HVAC system operating at 50% capacity in ambient conditions of 68° F. Finally, the D point EER measures the energy efficiency ratio of the HVAC system operating at 25% capacity in ambient conditions of 65° F. Each of these EERs is then weighted and added together to generate the integrated energy efficiency ratio (IEER). Embodiments of the present disclosure include HVAC systems that improve the IEER by reducing power consumption at operating conditions less than full cooling capacity, for example, when a multi-compressor HVAC system operates with less than all of its compressors. In order to increase the integrated energy efficiency ratio, the HVAC systems described below include one or more valves capable of controlling the flow of refrigerant through one or more condensers. By shutting down one or more condensers, the HVAC systems are able to shut down the associated fans used to draw air over those condensers. Furthermore, the HVAC systems below may also include a baffle between the condensers and their associated fans. The baffle focuses or guides airflow drawn by one or more fans over the operating condenser, which increases heat rejection from the operating condenser(s) and thus the overall efficiency of the HVAC system.

FIG. 5is a schematic of an embodiment of an HVAC system120. As illustrated, the HVAC system120is a two pipe HVAC system. The term “two pipe” refers to an HVAC system where multiple compressors122receive refrigerant through a single return pipe or conduit124and supply refrigerant through a single supply pipe or conduit126. A single return pipe124and a single supply pipe126enable the HVAC system120to include less piping and thus may reduce the overall cost of the system. However, when operating the HVAC system120at less than 100% capacity, in other words shutting down one or more of the compressors122, the HVAC system120is unable to use the full capacity of downstream components such as the condensers128and evaporators130. One or more of the condensers128and evaporators130may therefore be shut down/closed off and the refrigerant may be diverted away from those condensers128and evaporators130that are not operating. As will be described in detail below, the HVAC system120includes a controller132capable of controlling one or more valves to shut down one or more of the condensers128and evaporators130. In addition to controlling the flow of refrigerant through one or more condensers128and one or more evaporators130, the controller132is able to control operation of one or more fans134to reduce power consumption when one or more of the condensers128are not in use. This ability enables the HVAC system120to save energy when operating at less than 100% capacity and may therefore increase the IEER efficiency rating of the HVAC system120.

The refrigeration loop of the HVAC system120begins with the compressors122. As illustrated, the HVAC system120includes a first compressor136and a second compressor138that compress and drive refrigerant through the refrigeration loop. While two compressors122are shown, some embodiments may include additional compressors. After passing through the compressors122, the refrigerant flows through the single supply pipe or conduit126to the condensers128. In the condensers128, the refrigerant rejects heat, enabling the refrigerant to condense and change from a gaseous to a liquid state. To facilitate heat rejection by the refrigerant in the condensers128, the fans134draw/blow air across the condensers128. As illustrated, the HVAC system120includes a first condenser140and a second condenser142; however, the HVAC system120may include additional condensers128. After passing through the condensers128, the refrigerant flows to the evaporators130. But before the refrigerant enters the evaporators130, the refrigerant passes through thermal expansion valves (TXV) valves144which rapidly reduce the pressure and thus the temperature of the refrigerant. The cooled refrigerant then passes through the evaporators130where the refrigerant exchanges energy with a fluid, such as a supply air flow, flowing across the evaporators130. After passing through the evaporators130, the refrigerant enters the return pipe or conduit124which directs the refrigerant back to the compressors122, thereby restarting the refrigeration loop.

As explained above, the HVAC system120may operate at less than full capacity. For example, the HVAC system120may operate at 75%, 50%, 25% capacity. In order to operate at these reduced capacities, either compressor136or138may be shutdown. In some embodiments, the controller132may alternate operation between the two compressors136,138to use them more or less equally each time the HVAC system120operates at a reduced cooling capacity. Because a single compressor122is unable to move as much refrigerant through the HVAC system120, the controller132diverts the refrigerant away from one of the condensers128and one of the evaporators130. The controller132does this by controlling solenoid valves146and148. As illustrated, by closing solenoid valve146, the HVAC system120diverts refrigerant away from the condenser140and sends the refrigerant through only the condenser142. Similarly, when the controller132closes the solenoid valve148, the HVAC system120diverts refrigerant away from the evaporator150and sends the refrigerant through only the evaporator152.

To facilitate heat transfer from the refrigerant as it flows through the condensers128, the HVAC system120includes the fans134that draw air across the condensers128. As the air flows across the condensers128heat is transferred from the refrigerant to the surrounding air. As illustrated, the condensers140,142are serviced by respective fans154,156. For example, the condenser140may be serviced with one or more fans154, and the condenser142may be serviced with one or more fans156. In order to reduce power consumption when the HVAC system120is operating at a reduced capacity, such as less than 100%, the controller132turns off the fans154that draw air over the condenser140. Because the condenser140does not receive refrigerant when the HVAC system120is operating at a reduced capacity, drawing air over the condenser140may waste power, and thus reduce the overall efficiency of the HVAC system120. However, because the condenser142still receives refrigerant, the controller132still operates the fans156to draw air across the condenser142.

As illustrated, the HVAC system120includes a baffle158that facilitates heat transfer from the condenser142when the condenser140is shutdown, the HVAC system120includes a baffle158. The baffle158reduces and/or blocks airflow between the condensers140,142and their respective fans154,156. Without the baffle158, the air flow generated by the fans156may cause the fans154to rotate. If the fans154are able to rotate they may draw air away from condenser142, thus increasing power consumption by the fans156that service the condenser142. In other words, the fans154would have to work harder to maintain a desired amount of heat transfer from the refrigerant to the surrounding air through the condenser142. The baffle158is therefore able to reduce/block fluid communication between the condensers128, and thus focus or guide air drawn/blown by the fans134over respective condensers128. Accordingly, by providing the baffle158and shutting down the fans154servicing the condenser140, the HVAC system120is able to save energy when operating at less than 100% of its cooling capacity.

As illustrated, the baffle158defines a length160that is greater than a length162of the condensers128to reduce and/or block airflow between the condensers128. However, in some embodiments, the length160of the baffle158may be equal to the length162of the condensers128to reduce and/or block airflow between the condensers128.

The controller132may include a processor164and a memory166used in controlling the compressors122, fans134, and valves. In operation, the processor164executes software stored by the memory166to control the HVAC system120. The processor164may include one or more multiple microprocessors, one or more “general-purpose” microprocessors, one or more special-purpose microprocessors, and/or one or more application specific integrated circuits (ASICS), or some combination thereof. For example, the processor164may include one or more reduced instruction set (RISC) processors.

The memory166may include a volatile memory, such as random access memory (RAM), and/or a nonvolatile memory, such as read-only memory (ROM). The memory166may store a variety of information and may be used for various purposes. For example, the memory166may store processor executable instructions, such as firmware or software, for the processor164to execute. The memory may include ROM, flash memory, a hard drive, or any other suitable optical, magnetic, or solid-state storage medium, or a combination thereof. The memory may store data, instructions, such as software or firmware for controlling the HVAC system120, and any other suitable data.

FIG. 6is a schematic of an embodiment of an HVAC system170. The HVAC system170is a two pipe HVAC system with the compressors122receiving refrigerant through the single return pipe or conduit124and supply refrigerant through the single supply pipe or conduit126. When the HVAC system170operates at a reduced capacity, such as less than 100% capacity, the HVAC system170is unable to use the full capacity of downstream components such as the condensers128and evaporators130. One or more of the condensers128and evaporators130may therefore be shut down/closed off and the refrigerant diverted away from those condensers128and evaporators130that are not operating. In order to alternate between the condensers128and evaporators130, the HVAC system170includes a controller132that controls the flow of refrigerant with valves. The controller132also controls operation of one or more fans134. By controlling operation of the fans134, the HVAC system170is able to reduce power consumption when one or more of the condensers128are not in use. The HVAC system170is therefore able to save energy when operating at less than 100% of its cooling capacity.

The refrigeration loop of the HVAC system170begins with the compressors122. While two compressors136and138are shown, in some embodiments the HVAC system170may include additional compressors122. After passing through the compressors122, the refrigerant flows through the single supply pipe or conduit126which carries the refrigerant to the condensers128. In the condensers128, the refrigerant rejects heat, condensing the refrigerant from a gaseous to a liquid state. To facilitate heat rejection, the fans134draw/blown air across the condensers128. The HVAC system170includes the first condenser140and the second condenser142; however, the HVAC system170may include additional condensers128. After passing through the condensers128, the refrigerant flows to the evaporators130. But before entering the evaporators130, the refrigerant passes through the TXV valves144which rapidly reduce the pressure and thus the temperature of the refrigerant. The cooler refrigerant then passes through the evaporators130where the refrigerant exchanges energy with the fluid flowing across the evaporators130. After passing through the evaporators130the refrigerant enters the return pipe or conduit124which guides refrigerant back to the compressors122restarting the refrigeration loop.

As explained above, the HVAC system170may operate at less than full cooling capacity. In order to operate at these reduced capacities either compressor136or138may be shutdown. In some embodiments, the controller132may alternate between the two compressors136,138each time the HVAC system170operates at a reduced cooling capacity, such as less than 100% of its cooling capacity. Because a single compressor122is unable to move as much refrigerant through the HVAC system170, the controller132diverts the refrigerant away from one of the condensers128and evaporators130. The controller132does this by controlling solenoid valves146,147,148, and149. As illustrated, by closing solenoid valve146and opening solenoid valve147, the HVAC system170diverts refrigerant away from the condenser140and into the condenser142. Likewise, if the controller132closes the solenoid valve147and opens solenoid valve148, the refrigerant is diverted away from the condenser142and into the condenser140. The controller132similarly controls the flow of refrigerant through the evaporators130. For example, if the controller132closes solenoid valve148and opens solenoid valve149, refrigerant is diverted away from the evaporator150and into the evaporator152. Likewise, if the controller132closes the solenoid valve149and opens solenoid valve148, the refrigerant is diverted away from the evaporator152and into evaporator150. In some embodiments, the controller132may alternate between the condensers128and/or the evaporators130each time the HVAC system170operates at less than 100% of its cooling capacity.

To facilitate heat transfer from the refrigerant, the HVAC system170includes the fans134that draw air across the condensers128. As the air flows across the condensers128heat is transferred from the refrigerant to the air. As illustrated, the condensers140,142are serviced by respective fans154,156. The condenser140is serviced with one or more fans154while the condenser142is serviced with one or more fans156. In order to reduce power consumption when the HVAC system170is operating at less than 100% of its cooling capacity, the controller132turns off the fans134servicing the unused condenser128. For example, if the condenser140is not being used, then drawing air over the condenser140wastes power reducing the overall efficiency of the HVAC system170. Accordingly, the controller132shuts down the fans154when the condenser140is not in use. Likewise, if condenser142is the unused condenser128then the controller132saves power by shutting down the fans156.

In order to increase the heat transfer from the operating condenser128, the HVAC system170includes a baffle158. The baffle158reduces and/or blocks air flow between the condensers140,142and their respective fans154,156. Without the baffle158, the operating fans134may cause the non-operating fans134to spin backwards. If the non-operating fans134spin in the opposite direction they may draw air away from the operating condenser128increasing power consumption by the operating fans134as they work to maintain a desired amount of heat transfer from the operating condenser128. Thus by providing the baffle158, the HVAC system170may reduce power consumption by the fans134when operating at less than 100% of its cooling capacity.