Method and apparatus for calculating super heat in an air conditioning system

• US 5,666,815 A
• Filed: 11/18/1994
• Issued: 09/16/1997
• Est. Priority Date: 11/18/1994
• Status: Expired due to Term

• Current Assignee: Cooper-Atkins Corporation (Emerson Electric Company)
• Original Assignee: Cooper-Atkins Corporation (Emerson Electric Company)
• Inventors: Aloise, Arthur
• Primary Examiner(s): Tanner, Harry B.
• Application Number:
  US08/342,343
• Time in Patent Office: 1,033 Days
• Field of Search: 62/125, 62/126, 62/127, 62/129, 62/225
• US Class Current: 62/129
• CPC Class Codes: F24F 11/30 for purposes related to the operation of the system, e.g. for safety or monitoring
• CPC Class Codes: F24F 11/62 characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
• CPC Class Codes: F24F 2140/12 Heat-exchange fluid pressure
• CPC Class Codes: F25B 2600/21 Refrigerant outlet evaporator temperature
• CPC Class Codes: G05D 23/1917 using digital means

Abstract

A super heat calculator for air conditioning systems comprising a microprocessor, a control panel, a temperature sensor, and a pressure sensor. Vapor pressure models for all expected air conditioning refrigerants are stored in a data storage unit of the microprocessor. Positioning a rotary switch on the control panel directs the microprocessor to utilize the vapor pressure model associated with the refrigerant assigned to the switch position. The temperature sensor and pressure sensor are installed between the evaporator and compressor of the air conditioning system. The temperature and pressure signals are sent to a dual slope analog to digital converter located in the control panel. The temperature of the refrigerant is automatically displayed when the calculator is turned on. Pressing the SUPER-HEAT button on the control panel initiates calculation of the degree of super heat. The microprocessor reads the refrigerant temperature and pressure values and stores them in the storage unit. The data processor accesses the vapor pressure model that corresponds to the refrigerant selected by the rotary switch and calculates the vapor temperature which corresponds to the sensed refrigerant pressure by interpolation. The data processor then calculates the super heat value by subtracting the calculated vapor temperature from the value of the sensed refrigerant temperature.

Claims

1. Apparatus for calculating the degree of super heat in an air conditioning system, the air conditioning system containing one of a plurality of refrigerants, the apparatus comprising:

first temperature sensing means for sensing the temperature of the refrigerant and transmitting a first temperature signal proportional to the sensed temperature;

pressure sensing means for sensing the pressure of the refrigerant and transmitting a pressure signal proportional to the sensed pressure;

a computer platform including data processor means for performing arithmetic and logic operations on digitized data, data storage means coupled to said data processor means, for storing digitized data including instruction data and operand data, first input means for supplying instruction data to said data processor means, second input means for receiving and digitizing said first temperature signal and said pressure signal, said second input means supplying said digitized first temperature signal and said digitized pressure signal to said data processor means, said data storage means containing a stored computer program including modelling means for modelling the vapor pressure of the refrigerant at a plurality of vapor temperature points, said modelling means comprising a plurality of models wherein each of said models defines the vapor pressure of one of the refrigerants at a plurality of vapor temperature points, comparison means for comparing said digitized pressure signal to said model wherein said digitized pressure signal and said model define a vapor temperature value, and computing means for computing and transmitting a super heat value wherein said super heat value is the difference between said digitized first temperature signal and the vapor temperature value; and

display means for receiving and displaying said super heat value.

2. The apparatus of claim 1 where in said computer platform further comprise selection means for selecting a said model from said plurality of models.

3. The apparatus of claim 1 further comprising output means for recording at least some of the results of the arithmetic and logic operations of the data processor means.

4. The apparatus of claim 1 further comprising a second temperature sensing means for sensing the temperature of the refrigerant and transmitting a second temperature signal proportional to the sensed temperature.

5. The apparatus of claim 4 wherein said second input means receives and digitizes said second temperature signal, said second input means supplying said digitized second temperature signal to said data processor means.

6. The apparatus of claim 5 further comprising a second comparison means for comparing said digitized first temperature signal to said digitized second temperature signal.

7. The apparatus of claim 1 wherein said first input means comprises a keypad having a plurality of input keys.

8. The apparatus of claim 4 wherein said first and second temperature sensing means each comprise a thermistor temperature probe.

9. The apparatus of claim 1 wherein said first temperature sensing means has a minimum range of approximately -40°

to 300°

F.

10. The apparatus of claim 9 wherein said first temperature sensing means has a minimum resolution of approximately 0.1°

F.

11. The apparatus of claim 1 wherein said pressure sensing means has a minimum range of approximately 0 to 300 psi.

12. The apparatus of claim 11 wherein said pressure sensing means has a minimum resolution of approximately 1 psi.

13. A method for calculating the degree of super heat in an air conditioning system containing one of a plurality of refrigerants, comprising the steps of:

providing a superheat measuring device comprising a computer platform having a stored computer program including a plurality of models, each of said models defining vapor pressure values of one of the refrigerants at a plurality of vapor temperature points;

selecting the model corresponding said one refrigerant;

measuring the temperature of the refrigerant and transmitting a temperature signal proportional to the sense temperature to the computer platform;

measuring the pressure of the refrigerant and transmitting a pressure signal proportional to the sensed pressure the computer platform;

comparing said pressure signal to said model to define a vapor temperature value; and

computing the difference between said temperature signal and said vapor temperature value to determine the heat value of the refrigerant.

14. A method for optimizing the of an air conditioning system containing one of a plurality of refrigerants, each of the refrigerants having an ideal super value when the refrigerant is between the evaporator and the compressor of air conditioning system, the method comprising the steps of:

providing a superheat measuring device comprising a computer platform having a stored computer program including of models, each of said models defining vapor pressure values of the refrigerants at a plurality of vapor temperature points;

selecting the model corresponding to said one refrigerant;

measuring the temperature of the refrigerant and transmitting a first temperature signal proportional to the sensed temperature to the computer platform;

measuring the pressure of the refrigerant and transmitting a pressure signal proportional to the sensed pressure to the computer platform;

comparing said pressure signal to said model to define a vapor temperature value;

computing the difference between said first temperature signal and said vapor temperature value to determine a super heat value;

displaying said computed super heat value;

comparing said computed super heat value with the ideal super heat value; and

adjusting the performance of the air conditioning unit.

15. Apparatus for optimizing the performance of an air conditioning system, the air conditioning system containing one of a plurality of refrigerants, the refrigerant having an ideal super heat value when the refrigerant is between the evaporator and the compressor of the air conditioning system, the apparatus comprising:

first temperature sensing means for sensing the temperature of the refrigerant and transmitting a first temperature signal proportional to the sensed temperature;

pressure sensing means for sensing the pressure of the refrigerant and transmitting a pressure signal proportional to the sensed pressure;

a computer platform including data processor means for performing arithmetic and logic operations on digitized data, data storage means coupled to said data processor means, for storing digitized data including instruction data and operand data, first input means for supplying instruction data to said data processor means, second input means for receiving and digitizing said first temperature signal and said pressure signal, said second input means supplying said digitized first temperature signal and said digitized pressure signal to said data processor means, said data storage means containing a stored computer program including a plurality of models wherein each of said models defines the vapor pressure of one of the refrigerants at a plurality of vapor temperature points, input means for selecting a said model corresponding to the refrigerant, comparison means for comparing said digitized pressure signal to said model wherein said digitized pressure signal and said model define a vapor temperature value, and computing means for computing and transmitting a super heat value wherein said super heat value is the difference between said digitized first temperature signal and the vapor temperature value; and

display means for receiving and displaying said computed super heat value;

wherein said computed super heat value is compared with the ideal super heat value and the performance of the air conditioning unit thereby adjusted.

16. The apparatus of claim 15 wherein said computer platform further comprises selection means for selecting a said model from said plurality of models.

17. The apparatus of claim 15 wherein said first and second temperature sensing means each comprise a thermistor temperature probe having a minimum range of approximately -40°

to 300°

F. and a minimum resolution of approximately 0.1°

F.

18. The apparatus of claim 15 wherein said pressure sensing means has a minimum range of approximately 0 to 300 psi and a minimum resolution of approximately 1 psi.