Heating, ventilation, and air-conditioning systems and methods with bypass line

Abstract

A heating, ventilation, and air-conditioning system with a refrigeration circuit that includes a compressor fluidly, an outdoor heat exchanger fluidly connected downstream of the compressor, a cooling expansion valve fluidly connected downstream of the outdoor heat exchanger, an indoor heat exchanger fluidly connected downstream of the cooling expansion valve when operating in a cooling mode. A bypass line fluidly connects the circuit from a first location downstream of the outdoor heat exchanger and upstream of the cooling expansion valve to a second location downstream of the indoor heat exchanger and upstream of the compressor. Some of the refrigerant is flowable through the bypass line at the first location to bypass the cooling expansion valve and the indoor heat exchanger and recombinable with the refrigerant in the circuit at the second location to lower the compressor discharge temperature compared to not flowing the refrigerant through the first bypass line.

What is claimed is: 
     
         1 . A heating, ventilation, and air-conditioning (“HVAC”) system for use with a refrigerant, the HVAC system comprising:
 a closed loop circuit of tubing forming a refrigeration circuit; 
 a compressor fluidly connected to the circuit and operable to compress the refrigerant and discharge the refrigerant at a compressor discharge temperature; 
 an outdoor heat exchanger fluidly connected to the circuit downstream of the compressor while the HVAC system is in a cooling mode; 
 a cooling expansion valve fluidly connected in the closed loop circuit downstream of the outdoor heat exchanger in the cooling mode, the cooling expansion valve configured to reduce a pressure of the refrigerant flowing therethrough; 
 an indoor heat exchanger fluidly connected in the circuit downstream of the cooling expansion valve in the cooling mode; and 
 a first bypass line fluidly connecting the circuit from a first location downstream of the outdoor heat exchanger and upstream of the cooling expansion valve to a second location downstream of the indoor heat exchanger and upstream of the compressor, in the cooling mode, 
 wherein some of the refrigerant is flowable through the first bypass line at the first location to bypass the cooling expansion valve and the indoor heat exchanger and recombinable with the refrigerant in the circuit at the second location to lower the compressor discharge temperature as compared to not flowing the refrigerant through the first bypass line. 
 
     
     
         2 . The system of  claim 1 , wherein the first bypass line is sized to:
 bypass enough refrigerant to the second location when the compressor is operating at a high-pressure differential condition to maintain the compressor discharge temperature below a maximum threshold while not choking the refrigerant flow passing through the first bypass line; and   bypass a minimum refrigerant flow when the compressor is operating at normal operating conditions to avoid performance degradation of the HVAC system.   
     
     
         3 . The system of  claim 1 , wherein the system comprises a heat pump system comprising:
 a heating expansion valve fluidly connected in the circuit downstream of the indoor heat exchanger in a heating mode, the heating expansion valve configured to reduce a pressure of the refrigerant flowing therethrough; and   a reversing valve configured to reverse the flow of the refrigerant to change between the heating mode and the cooling mode,   wherein in the heating mode, the first location is downstream of the indoor heat exchanger and upstream of the heating expansion valve.   
     
     
         4 . The system of  claim 3 , further comprising a second bypass line fluidly connecting the circuit from a third location downstream of the indoor heat exchanger and upstream of the heating expansion valve to a fourth location downstream of the outdoor heat exchanger and upstream of the compressor, in the heating mode. 
     
     
         5 . The system of  claim 3 , wherein disposed within the first bypass line is a device selected from the group consisting of a restriction, a flexible restriction, a check valve, an adjustable check valve, an ON/OFF solenoid valve, a stepper motor solenoid valve, a pulse width modulation (PWM) solenoid valve, a mechanical valve adjustable by a temperature bulb, and a mechanical valve adjustable by a pressure tap. 
     
     
         6 . The system of  claim 1 , further comprising a heat pump system wherein the cooling expansion valve comprises a bi-flow expansion valve further configured to also reduce a pressure of the refrigerant flowing therethrough in a heating mode, the system further comprising:
 a reversing valve configured to reverse the flow of the refrigerant to change between the heating mode and the cooling mode; and   a second bypass line fluidly connecting the circuit from a third location downstream of the indoor heat exchanger and upstream of the bi-flow expansion valve to a fourth location downstream of the outdoor heat exchanger and upstream of the compressor, in the heating mode.   
     
     
         7 . The system of  claim 1 , wherein the first bypass line contains a flexible material comprising a variable diameter based on a pressure differential outdoor across the first bypass line. 
     
     
         8 . The system of  claim 1 , wherein the bypass line comprises a restriction. 
     
     
         9 . The system of  claim 1 , wherein the first bypass line comprises a check valve biased by a spring, wherein a pressure differential across the check valve opens the check valve to allow refrigerant to flow through the first bypass line. 
     
     
         10 . The system of  claim 1 , wherein the first bypass line comprises an adjustable check valve. 
     
     
         11 . The system of  claim 1 , further comprising a temperature sensor downstream of the compressor and wherein the first bypass line comprises a solenoid valve controllable based on the temperature of the refrigerant as measured by the temperature sensor and wherein the compressor downstream position comprises a discharge line of the compressor, a de-superheating portion of the outdoor heat exchanger, or a two-phase region of the outdoor heat exchanger. 
     
     
         12 . The system of  claim 1 , further comprising a temperature bulb connected to an output line of the compressor and wherein the first bypass line comprises a mechanical valve operable by the temperature bulb depending on the discharge temperature of the refrigerant discharged from the compressor. 
     
     
         13 . The system of  claim 1 , further comprising a pressure tap connected to an output line of the compressor and wherein the first bypass line comprises a mechanical valve connected to the pressure tap and operable by pressure of the refrigerant communicated from the pressure tap and wherein the compressor downstream position comprises a discharge line of the compressor, a de-superheating portion of the outdoor heat exchanger, or a two-phase region of the outdoor heat exchanger. 
     
     
         14 . A method of operating a heating, cooling, and air conditioning (HVAC) system, the method comprising:
 condensing high-pressure refrigerant in an outdoor heat exchanger of the HVAC system in a cooling mode of the HVAC system;   separating the high-pressure refrigerant at a first location downstream of the outdoor heat exchanger and upstream of a cooling expansion valve, wherein a first portion of the refrigerant flows through a first bypass line and a second portion of the refrigerant flows to the cooling expansion valve, when the HVAC system is in the cooling mode;   reducing the pressure of the second portion of the refrigerant exiting the condenser to a low-pressure refrigerant in the cooling expansion valve of the HVAC system, when the HVAC system is in the cooling mode;   evaporating the second portion of the refrigerant in an indoor heat exchanger of the HVAC system;   combining the second portion of the refrigerant from the indoor heat exchanger with the first portion of the refrigerant from the first bypass line at a second location downstream of the indoor heat exchanger and upstream of a compressor, in the cooling mode to form a combined refrigerant;   compressing the combined refrigerant with the compressor of the HVAC system, the compressor comprising a discharge temperature; and   lowering the discharge temperature of the compressor with the combined refrigerant as compared to not flowing the refrigerant through the first bypass line.   
     
     
         15 . The method of  claim 14 , further comprising:
 separating enough of the refrigerant when the compressor is operating at a high-pressure differential condition to maintain the discharge temperature of the compressor below a maximum threshold while not choking the refrigerant flow through the first bypass line; and   separating a minimum amount of the refrigerant flow when the compressor is operating at normal operating conditions to avoid performance degradation of the compressor.   
     
     
         16 . The method of  claim 14 , further comprising restricting the flow of the first portion of refrigerant through the first bypass line. 
     
     
         17 . The method of  claim 16 , wherein restricting the flow of the first portion of refrigerant is based on a temperature of the refrigerant at a compressor discharge, at the outdoor heat exchanger, or between the outdoor heat exchanger and the compressor. 
     
     
         18 . The method of  claim 14 , further comprising:
 reversing the flow of the refrigerant, in a heating mode, with a reversing valve;   condensing high-pressure refrigerant in the indoor heat exchanger of the HVAC system in the heating mode;   separating the high-pressure refrigerant at the first location such that a first portion of the refrigerant flows through the first bypass line and a second portion of the refrigerant flows to a heating expansion valve fluidly connected downstream of the indoor heat exchanger, when the HVAC system is in the heating mode, wherein in the heating mode, the first location is downstream of the indoor heat exchanger and upstream of the heating expansion valve;   reducing a pressure of the second portion of the refrigerant flowing through the heating expansion valve to a low-pressure refrigerant;   evaporating the second portion of the refrigerant in the outdoor heat exchanger;   combining in the heating mode, an output of the first bypass line and an output of the outdoor heat exchanger upstream of the compressor at the second location;   compressing the combined refrigerant with the compressor; and   lowering the discharge temperature of the compressor with the combined refrigerant as compared to not flowing the refrigerant through the first bypass line.   
     
     
         19 . The method of  claim 14 , further comprising:
 reversing the flow of the refrigerant, in a heating mode, with a reversing valve;   condensing high-pressure refrigerant in the indoor heat exchanger of the HVAC system in the heating mode;   separating the high-pressure refrigerant at a third location downstream of the indoor heat exchanger and upstream of a heating expansion valve such that a first portion of the refrigerant flows through a second bypass line and a second portion of the refrigerant flows to the heating expansion valve fluidly connected downstream of the indoor heat exchanger, when the HVAC system is in the heating mode;   reducing a pressure of the second portion of the refrigerant flowing through a heating expansion valve to a low-pressure refrigerant;   evaporating the second portion of the refrigerant in the outdoor heat exchanger;   combining in the heating mode, an output of the second bypass line and an output of the outdoor heat exchanger upstream of the compressor at a fourth location;   compressing the combined refrigerant with the compressor; and   lowering the discharge temperature of the compressor with the combined refrigerant as compared to not flowing the refrigerant through the second bypass line.   
     
     
         20 . The method of  claim 19 , further comprising tuning the second bypass line to specific compressor operating conditions.