HVAC heat exchanger freeze control means

Abstract

A method and HVAC system having a heat exchanger and a device for adjusting parameters of an HVAC system via an algorithm, in an incremental or linear fashion, is provided. Various aspects provide a method for altering and/or controlling auxiliary evaporator temperature in an automotive HVAC unit and an HVAC system having an HVAC unit with a blower and a temperature sensing device capable of detecting temperatures that drop below a desired minimum operating temperature and sending a corresponding signal, ultimately preventing evaporator freezing.

1 . A method for regulating the temperature of a heat exchanger of an automotive HVAC system, having an HVAC module with a blower and a temperature sensing device capable of detecting temperatures that drop below a desired minimum operating temperature, the method comprising: 
 measuring the surface temperature or the discharge air temperature of the heat exchanger using the temperature sensing device;    sending a signal from the temperature sensing device to a control logic device;    detecting temperature conditions where the temperature in or around the heat exchanger drops below the minimum operating temperature;    calculating a response to send as a command from the control logic device to the blower motor or blower motor controller based on the signal; and    increasing incrementally or linearly the airflow volume from the blower device in response to the response signal;    thereby altering the operating temperature of the heat exchanger by the increased flow of air through the heat exchanger, and preventing the temperature of the heat exchanger from reaching, or being sustained at, the minimum operating temperature in normal operation.    
   
   
       2 . The method according to  claim 1  wherein the heat exchanger is located in an auxiliary HVAC module and wherein the temperature sensing device is located on or in the auxiliary HVAC module.  
   
   
       3 . The method according to  claim 2  wherein the control logic device is located in an auxiliary or main control head of the HVAC module.  
   
   
       4 . The method according to  claim 2  wherein the temperature sensing device is downstream of the evaporator.  
   
   
       5 . The method according to  claim 4  wherein the defined threshold level is correlated to the freezing point of the auxiliary heat exchanger, and wherein the auxiliary heat exchanger is an evaporator.  
   
   
       6 . The method according to  claim 5  wherein a blower device parameter is regulated in its response by varying a supply voltage or a command signal.  
   
   
       7 . The method according to  claim 6  wherein the blower device has a motor, and wherein the parameter regulated or controlled is the speed, current or voltage of the blower motor.  
   
   
       8 . The method according to  claim 7  wherein the control logic device uses control logic that involves implementation and validation of software algorithms used for blower control.  
   
   
       9 . The method according to  claim 5  wherein the temperature sensing device is located downstream or in the discharge air face of the auxiliary evaporator.  
   
   
       10 . The method according to  claim 6  wherein the temperature sensing device is a thermistor, a thermocouple, or an infra-red sensor.  
   
   
       11 . The method according to  claim 6  wherein the HVAC system has other devices that are regulated by one or more control parameters other than blower device parameters.  
   
   
       12 . The method according to  claim 11  wherein the output of the temperature sensing device affects one or more control parameters other than blower device parameters, as well as at least one blower device parameter.  
   
   
       13 . The method according to  claim 10  wherein the auxiliary evaporator core average temperature is operated at a time averaged temperature above 0° centigrade.  
   
   
       14 . An HVAC system, comprising: 
 an auxiliary HVAC module having a temperature sensing device and an evaporator;    a blower device; and    a control device;    wherein the temperature sensing device sends out a signal to the control device to ultimately prevent freezing of the evaporator.    
   
   
       15 . The HVAC system according to  claim 14  wherein the temperature sensing device is downstream the evaporator, and the blower device provides for discharged air through the evaporator.  
   
   
       16 . The HVAC system according to  claim 15  wherein the control device implements a control method to generate a command or commands to the blower device.  
   
   
       17 . The HVAC system according to  claim 16  wherein the command or commands are such that the amount of airflow provided by the blower device is affected in an incremental or linear fashion.