Control arrangement for a cooling apparatus

• US 5,749,238 A
• Filed: 02/14/1997
• Issued: 05/12/1998
• Est. Priority Date: 08/27/1994
• Status: Expired due to Term

• Current Assignee: Danfoss A/S
• Original Assignee: Danfoss A/S
• Inventors: Schmidt, Frede
• Primary Examiner(s): Bennett, Henry A.
• Assistant Examiner(s): TINKER, SUSANNE CHRISTINE
• Application Number:
  US08/793,817
• Time in Patent Office: 452 Days
• Field of Search: 62/211, 62/223, 62/222, 62/225, 62/213
• US Class Current: 62/211
• CPC Class Codes: F25B 2400/075 with parallel compressors
• CPC Class Codes: F25B 2400/22 Refrigeration systems for supermarkets
• CPC Class Codes: F25B 2600/21 Refrigerant outlet evaporator temperature
• CPC Class Codes: F25B 2600/2513 Expansion valves
• CPC Class Codes: F25B 41/34 with the valve member being actuated by electric means, e.g. by piezoelectric actuators
• CPC Class Codes: F25B 49/022 Compressor control arrangements
• CPC Class Codes: F25B 5/02 arranged in parallel
• CPC Class Codes: Y02B 30/70 Efficient control or regulation technologies, e.g. for control of refrigerant flow, motor or heating

Abstract

A control arrangement for cooling of an apparatus comprising a compressor, a condenser, and at least one branch with an expansion valve and an evaporator in series, contains a controller, a superheat temperature measuring device, and an ambient temperature sensor. The controller controls the expansion valve for maintaining the superheat temperature substantially at the desired value. The flow of coolant to the evaporator is controlled by the signal from the temperature sensor for maintaining the ambient temperature constant. The controller operates continuously and in two operating modes in which the first mode the superheat temperature is controlled to the maximum admissible state of fill of liquid coolant in the evaporator and is switchable to a second mode in which the state of fill of liquid coolant is controlled by the expansion valve.

Claims

1. A control arrangement for a cooling apparatus having a cooling circuit in which a compressor, a condenser and at least one branch with an expansion valve and a downstream evaporator are connected in series, the cooling apparatus further having a controller, a measuring device connected to the controller for measuring superheat temperature of the vapor of a liquid coolant evaporated in the evaporator and a sensor connected to the controller for sensing ambient temperature of the evaporator, the controller being connected to the expansion valve for controlling the expansion valve in dependence on a difference in a desired value and actual value of the superheat temperature for the purpose of reducing the difference, and flow of liquid coolant to the evaporator being controllable in dependence on the measured value of the ambient temperature for the purpose of maintaining the ambient temperature at a constant value, the controller having a continuous action, and the controller being switchable between a first operating mode in which the superheat refrigeration temperature is reduced while complying with the maximum admissible state of fill of liquid coolant in the evaporator and, after a desired refrigeration temperature is reached, a second operating mode in which the state of fill of liquid coolant in the evaporator is controlled by the expansion valve for the purpose of maintaining the refrigeration temperature.

2. A control arrangement according to claim 1, in which, when a minimum value of the superheat temperature is exceeded during the second operating mode, the controller is switchable to control of the superheat temperature to above the minimum value.

3. A control arrangement according to claim 1, in which the expansion valve is electronically controllable and the controller is an electronic controller.

4. A control arrangement according to claim 3, in which, for several branches lying parallel in the cooling circuit, each having an expansion valve and evaporator, a compressor of adjustable output is allocated to all branches jointly and each expansion valve has its own of said controllers.

5. A control arrangement according to claim 2, in which the expansion valve is electronically controllable and the controller is an electronic controller.

6. A control arrangement according to claim 5, in which, for several branches lying parallel in the cooling circuit, each having an expansion valve and evaporator, a compressor of adjustable output is allocated to all branches jointly and each expansion valve has its own of said controllers.

7. A control arrangement according to claim 1, in which, for several branches lying parallel in the cooling circuit, each having an expansion valve and evaporator, a compressor of adjustable output is allocated to all branches jointly and each expansion valve has its own of said controllers.