Method and system to prevent frost accumulation in an hvac system

Abstract

The present disclosure relates to a method of preventing accumulation of frost on a heat exchange system. The method includes steps for monitoring the temperature of a heat exchanger, comparing the temperature to the dew point of ambient air, and recalibrating the temperature of the heat exchange by adjusting refrigerant flow rate to meet or exceed the temperature of the dew point of ambient air.

What is claimed is: 
     
         1 . A method to prevent accumulation of frost on a heat exchanger in a refrigeration cycle system, the method comprising the steps of:
 measuring a saturated suction temperature of a refrigerant entering the heat exchanger;   measuring a dew point of an ambient air flow moving through the heat exchanger;   comparing the saturated suction temperature to the dew point of the ambient air flow;   recalibrating a mass flow rate of the refrigerant in the refrigeration cycle system when the saturated suction temperature is less than the dew point of the ambient air flow and a freezing temperature of water, wherein the recalibrating step comprises:
 instructing a compressor within the refrigeration cycle system to decrease the mass flow rate of the refrigerant in order to increase the saturated suction temperature of the refrigerant entering the heat exchanger; 
 taking another measurement of saturated suction temperature of the refrigerant; and 
 repeating the instructing and measuring steps until the saturated suction temperature is greater than or equal to at least one of the dew point of the ambient air flow or the freezing temperature of water. 
   
     
     
         2 . The method of  claim 1 , wherein the measuring the saturated suction temperature step comprises:
 orienting a pressure sensor upstream of an entrance of the compressor;   measuring a saturated suction pressure of the refrigerant flowing into the compressor; and   calculating the saturated suction temperature of the refrigerant from the measured saturated suction pressure of refrigerant.   
     
     
         3 . The method of  claim 1 , wherein prior to measuring the dew point of ambient air flow, the method comprises the step of orienting a dew point sensor downstream of the compressor. 
     
     
         4 . The method of  claim 1 , the method further comprising the step of continuously recycling refrigerant fluid throughout the refrigeration cycle system, wherein the refrigeration cycle system comprises:
 an evaporator in fluid connection with the compressor, the evaporator being oriented downstream of the compressor;   a pressure sensor upstream of the compressor to measure the pressure of refrigerant entering the compressor; and   a dew point sensor downstream of the compressor to measure the dew point of the ambient air flow moving through the evaporator.   
     
     
         5 . The method of  claim 1 , further comprising the step of increasing the mass flow rate of refrigerant in the refrigeration cycle system when the saturated suction temperature is greater than one of the dew point of the ambient air flow and the freezing temperature of water. 
     
     
         6 . The method of  claim 1 , further comprising the step of maintaining the mass flow rate of refrigerant within the refrigeration cycle system when the saturated suction temperature is greater than one of the dew point of the ambient air flow and the freezing temperature of water. 
     
     
         7 . The method of  claim 1 , further comprising the steps of orienting a condenser and expansion valve downstream of the compressor and upstream of an evaporator within the refrigeration cycle system. 
     
     
         8 . A refrigeration cycle system for preventing an accumulation of frost, the system comprising:
 a compressor and an evaporator in fluid connection, wherein the evaporator is downstream of the compressor;   a refrigerant for circulation through the refrigeration cycle system;   a suction pressure sensor upstream of the compressor to measure the pressure of refrigerant entering the compressor;   a dew point sensor disposed to measure the dew point of an ambient air flow entering the evaporator;   a speed control sensor disposed on the compressor to measure a flow rate of the refrigerant through the refrigerant cycle system; and   a controller operatively connected to the suction pressure sensor, dew point sensor, and speed control sensor, wherein the controller instructs the compressor to modulate the flow rate of the refrigerant flowing through the refrigerant cycle system based on measurements from the suction pressure sensor, dew point sensor, and speed control sensor.   
     
     
         9 . The system of  claim 8 , further comprising a condenser in fluid connection with the compressor and evaporator, wherein the condenser is downstream of the compressor and upstream of the evaporator. 
     
     
         10 . The system of  claim 9 , further comprising an expansion device in fluid connection with the compressor and evaporator, wherein the expansion device is downstream of the condenser and upstream of the evaporator. 
     
     
         11 . The system of  claim 8 , wherein the controller converts pressure measured by the suction pressure sensor into a saturated suction temperature of the refrigerant and compares the saturated suction temperature of the refrigerant to the dew point measured by the dew point sensor. 
     
     
         12 . The system of  claim 11 , wherein the controller instructs the compressor to decrease the flow rate of refrigerant through the refrigerant cycle system when the dew point is greater than the saturated suction temperature. 
     
     
         13 . The system of  claim 11 , wherein the dew point sensor measures the temperature of the air flow entering the evaporator simultaneously with the dew point of the air flow entering the evaporator. 
     
     
         14 . The system of  claim 13 , wherein the controller instructs the compressor to decrease the flow rate of refrigerant through the refrigerant cycle system where the saturated suction temperature is less than both of the dew point and 32 degrees Fahrenheit. 
     
     
         15 . The system of  claim 13 , wherein the controller instructs the compressor to maintain or increase the flow rate of refrigerant through the refrigerant cycle system where the saturated suction temperature is not less than both of the dew point and 32 degrees Fahrenheit. 
     
     
         16 . The system of  claim 8 , wherein the refrigerant is continuously recycled into the compressor after flowing through the refrigerant cycle system.