Heatcraft Inc.

Gregory S Derosier

Ira Zelman Richter

James A Kitchen

An improved defrost controller is provided for a space cooling system of the type having an evaporator in heat exchange relationship with a space to be cooled, a condenser external to the space, a compressor for circulating heat transfer fluid between the evaporator and condenser, an expansion valve located between an outlet from the condenser and an inlet to the evaporator, and a defroster operatively associated with the evaporator. The expansion valve is positionable in a plurality of positions between a fully open position and a fully closed position to maintain a desired level of superheat across the evaporator. The defrost controller monitors the expansion valve position and activates the defroster in response to the expansion valve being in a more closed position than a predetermined defrost target position. The defrost controller is further operable to prevent defrosting from occurring at times other than predetermined allowed defrost times, even if the position of the expansion valve indicates a demand for defrost. The defrost target position is adjusted in response to changes in selected system operating parameters. Further, at each allowed defrost time, the controller determines whether defrosting can be deferred until a next allowed defrost time, based on the then current rate of degradation in evaporator performance. If the then current rate of degradation indicates that defrosting cannot be deferred to the next allowed defrost time, the controller activates the defroster, even if a demand for defrost is not indicated.

Defrost control for space cooling system

A heat exchanger coil is comprised of plural metal tubes of generally circular cross-section, plural heat transfer enhancing fins and plural relatively flat metal support plates, each of which has plural first holes and plural second holes arranged in parallel rows. The tubes are laced through the respective holes in the plates and through aligned holes in the fins such that the tubes extend generally at right angles to the respective planes of the plates and fins. In one embodiment, each plate is cut to define two discrete flexible sections and a resilient arm for flexibly coupling one of the two sections of each plate with a relatively fixed portion of the corresponding plate. The first holes, which are oversized relative to the outside diameter of the tubes laced therethrough, are formed in both the relatively fixed portion and the two flexible sections of each plate. The second holes, which are smaller in diameter than the first holes, are formed only in the two flexible sections of each plate. The tubes extending through the second holes are in contact with the corresponding flexible sections such that the flexible sections provide support for all of the tubes and fins of the heat exchanger coil. The tubes extending through the first holes are able to float with respect to the plates because of the oversized first holes, while the tubes extending through the second holes are constrained to move relative to the plates along with the corresponding flexible sections.

Heat exchanger with flexible tube support

Apparatus for providing integrated control of a space cooling system is disclosed. The apparatus receives inputs from a plurality of temperature sensors, including a temperature sensor for measuring evaporator superheat, space temperature and compressor discharge temperature. The control apparatus incrementally adjusts the position of the cooling system expansion valve to regulate evaporator superheat and compressor discharge temperature and cycles the outdoor condenser fan on and off to raise condenser pressure in response to a low condenser pressure condition. In one embodiment, the cooling system includes a plurality of evaporators and a corresponding plurality of controllers electrically interconnected in a series loop for controlling the expansion valves and defrost heaters associated with the respective evaporators. One of the controllers functions as a master controller and receives inputs from the space temperature sensor and the compressor discharge temperature sensor as well as from the temperature sensors associated with the corresponding evaporator. The master controller activates and deactivates the cooling cycles in response to the inputs from the space temperature sensor. Both the master controller and each slave controller separately control the corresponding expansion valve and defroster. The master controller also initiates the system defrost cycle. However, once the defrost cycle is initiated, each slave controller controls the defrost cycle for its corresponding evaporator.

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Conyers, GA, United States of America

Gregory S Derosier