Thermo King Corporation

David H Taylor

Lee J Erickson

Lars Ivan Sjoholm

Peter W Freund

Sung L Kwon

Leland L Howland

Herman H Viegas

Roland L Roehrich

Hendrie J Grant

Rodney H Volk

Russell M Luck

Allan I Bennett

Lowell B Naley

Cynthia J Satterness

Lawrence J Shirek

Lars I Sjoholm

A refrigeration system of the type having an economizer cycle is provided with a null cycle, in addition to heating and cooling cycles, without shutting a compressor prime mover down, to preserve air flow in a conditioned space. First, second and third controllable valves respectively: (1) select main and auxiliary condensers, (2) open and close a liquid line, and (3) open and close a line which provides a warm liquid to an economizer heat exchanger. The valves are controlled in at least one predetermined open/close pattern during a null cycle, and preferably in a plurality of selectable predetermined open/close patterns, to provide a null cycle at any instant which substantially matches the net heat gain or loss taking place in the conditioned space. Thus, the temperature of the served space will be more apt to remain in a null temperature range close to set point, providing smoother and more accurate control over the temperature of the conditioned space for longer shelf life of perishables stored therein. The system achieves the latter by controlling cooling circulation in the compressor oil cooler.

Methods and apparatus for operating a refrigeration system characterized

A refrigeration system associated with a conditioned space to be controlled to a predetermined set point temperature via heating and cooling cycles. The refrigeration system includes a fluid flow path through which a predetermined liquid is circulated. The fluid flow path includes a slush tank and first and second heat exchangers, with cryogen from a supply vessel being expanded into liquid disposed in the slush tank. The first heat exchanger is disposed to condition the air of the conditioned space, and the second heat exchanger is in heat exchange relation with heating apparatus. The first heat exchanger and slush tank are interconnected when the conditioned space requires a cooling cycle, and the first and second heat exchangers are interconnected when the conditioned space requires a heating cycle. Cryogen of the cryogenic cooling apparatus is thus not expended to heat the conditioned space, or for defrosting purposes.

Air conditioning and refrigeration apparatus utilizing a cryogen

A refrigeration system associated with a conditioned space to be controlled to a predetermined set point temperature via heating and cooling cycles. The refrigeration system includes a fluid flow path through which a predetermined fluid is circulated. The fluid flow path includes first, second and third heat exchangers. The first heat exchanger is disposed to condition air of the conditioned space, the second heat exchanger is in heat exchange relation with cryogenic cooling apparatus, and the third heat exchanger is in heat exchange relation with heating apparatus. The first and second heat exchangers are interconnected when the conditioned space requires a cooling cycle, and the first and third heat exchangers are interconnected when the conditioned space requires a heating cycle. Cryogen of the cryogenic cooling apparatus is thus not expended to heat the conditioned space, nor used for defrosting purposes.

A refrigeration system of the type having an economizer cycle is provided with a null cycle, in addition to heating and cooling cycles, without shutting a compressor prime mover down, to preserve air flow in a conditioned space. First, second and third controllable valves respectively: (1) select main and auxiliary condensers, (2) open and close a liquid line, and (3) open and close a line which provides a warm liquid to an economizer heat exchanger. The valves are controlled in at least one predetermined open/close pattern during a null cycle, and preferably in a plurality of selectable predetermined open/close patterns, to provide a null cycle at any instant which substantially matches the net heat gain or loss taking place in the conditioned space. Thus, the temperature of the served space will be more apt to remain in a null temperature range close to set point, providing smoother and more accurate control over the temperature of the conditioned space for longer shelf life of perishables stored therein.

Methods and apparatus for operating a refrigeration system

A transport refrigeration system having a dehumidifying mode. During the dehumidifying mode, a main or primary condenser is effectively removed from the active refrigerant circuit and an auxiliary or secondary condenser located in a conditioned air flow path performs the condensing function. This arrangement enables an evaporator in the air flow path to continue to cool and remove moisture from the conditioned air after a predetermined set point temperature has been reached, without a significant reduction in temperature of the conditioned air returned to a served space, as heat removed from the conditioned air by the evaporator is returned to the conditioned air by the secondary condenser.

Transport refrigeration system with dehumidifier mode

A transport refrigeration system, and method of operating same, in which a maximum operating pressure expansion valve and a secondary condenser are used to enhance hot gas heating cycles initiated to hold a predetermined temperature set point, and hot gas defrost cycles. The secondary condenser is disposed in an evaporator section of the refrigeration system, with hot discharge gas from a compressor being directed to the secondary condenser during heating and defrost cycles. A sufficient supply of refrigerant for heating and defrost cycles is ensured by injecting refrigerant from a receiver and condenser into an active heat cycle refrigerant circuit, when the active refrigerant is insufficient to build the pressure on the low pressure side of the refrigeration system to a value sufficient to close the maximum operating pressure expansion valve and the compressor suction pressure is less than the receiver/condenser pressure.

Transport refrigeration system with secondary condenser and maximum

A refrigeration system, and method of operating same, in which an economizer heat exchanger, normally used in conjunction with an intermediate port of a refrigerant compressor to cool the main refrigerant flow from a receiver to an evaporator to enhance the refrigerant cooling cycle, is caused to function as an evaporator during a hot gas heating cycle. The economizer heat exchanger is caused to function as an evaporator by adding heat thereto during a heating cycle, and by establishing an alternate liquid line, effective during a heating cycle, which includes the economizer heat exchanger. When the compressor is driven by an internal combustion engine, engine coolant may be used to add the necessary heat to the economizer heat exchanger during a heating cycle.

Method and apparatus for operating a refrigeration system

Disclosed is a method of measuring the depletion of basic additives in a lubricating oil. A sensor is immersed into the oil, an electric current is passed through the sensor, and the resistance of the sensor is measured. The sensor is made of copper, lead, mixtures of copper and lead, copper alloys, lead alloys, or mixtures thereof. Also disclosed is apparatus for indicating when the basic additives in a lubricating oil have been depleted. The apparatus consists of a sensor which is immersed in the oil, a first pair of electrodes for passing an electric current through the sensor, a second pair of electrodes for measuring the electrical resistance of the sensor, and an indicator for indicating when the electrical resistance has increased to a predetermined amount.

Measurement of the depletion of basic additives in lubricating oil

A method of operating a transport refrigeration system having a six cylinder compressor and a prime mover operable at a selected one of low and high speeds, to control the temperature of a served space by cooling and hot gas heating modes. Below a set point temperature 100, system heating capacity is controlled at the low compressor speed by the step 127 of unloading compressor cylinders and the step 129 of reloading compressor cylinders. A temperature rise of the served space above a set point temperature 106 controls cooling capacity by a combination of alternative steps 135, 137, 139, 141, and 143 which may or may not change the number of loaded compressor cylinders, and may or may not change compressor speed, based upon two predetermined trigger events which relate to what the temperature of the served space does relative to time 136 and 142, a set point temperature 106, and a temperature 108 above set point which is normally associated with a change in compressor speed.

Method of operating a transport refrigeration system having a six

A transport refrigeration system using a three-way valve 14 for either cooling mode operation and defrost and/or heating mode operation is provided with a thermal storage sink 28 having first and second heat exchangers 26 and 52 and a heat exchange medium 30 therein which serves to sub-cool refrigerant in its passage to the evaporator 36 in a cooling mode, and which serves to evaporate refrigerant in heat exchanger 52 in a defrost mode after the refrigerant has passed through the defrost heat exchanger 42 for defrosting evaporator 36. The stored heat in the medium 30 in the sink serves to hasten the defrost cycle.

Transport refrigeration system with thermal storage sink

A transport refrigeration unit of the mechanical refrigeration type and including a start-stop mode of operation is driven by an engine 20 which is coupled through belt 34 to a common shaft 32 for the condenser fan 26 and evaporator fan 30, through a clutch 38 which is selectively operable to drive the shaft 32 when the engine 20 is operating, and to decouple from the shaft 32 when the engine 20 is not operating so that ram air pressure to the condenser fan will in turn drive the evaporator fan to provide at least some air circulation in the interior space of the trailer.

Transport refrigeration unit with evaporator fan drive using ram air

A refrigerated trailer 10 which is subject to having a restricted normal return air flow path back to the refrigeration unit 24 through the suction space 46 in communication with the return air inlet 34 of the unit, due to volume and arrangement of the load 42, is provided with secondary air return ducts 48 and 50 which are also in communication with the suction space 46 to ensure an adequate return air flow to the unit and thereby also assuring an adequate discharge of air to the rear 22 of the trailer.

Growing community of inventors

Minneapolis, MN, United States of America

David H Taylor