US3527289A - Temperature control unit - Google Patents

Description

Sept 3, 1970 J. K. FOESSL 3,527,289

TEMPERATURE CONTROL UNIT Filed Dec. 16, 1968 3 Sheets-Sheet 1 INVENTOR John K. FUESSL ATTORNEYS P 8, 1970 J. K. FOESSL. 3,527,289

TEMPERATURE CONTROL UNIT Filed Dec. 16, 1968 3 Sheets-Sheet 2 TEMP OVERRIDE COMPRESSOR 58 TEMP. 1

RECORDER DE-FROST CONTROL HYDRAULIC FLUID RESERVOIR 24 INVENTOR John K. FOESSL ATTORNEYS United States Patent 3,527,289 TEMPERATURE CONTROL UNIT John K. Foessl, Montreal, Quebec, Canada, assignor to Galt Equipment Limited, Candiac, Quebec, Canada Filed Dec. 16, 1968, Ser. No. 783,832 Claims priority, application 2Canada, July 26, 1968,

Int. (:1. F25b 29/00 U.S. Cl. 165-29 13 Claims ABSTRACT OF THE DISCLOSURE the container.

This invention relates to temperature control equipment and particularly to a self-contained temperature control unit incorporating a refrigeration unit of the vapour compression type.

The self-contained temperature control unit of the invention is particularly adaptable for fitting into a cargo container for maintaining the interior of the container within a specified temperature range. Self-contained temperature control units of this type are described in U. S. Pat. No. 3,367,131 issued on Feb. 6, 1968, to John K. Foessl. The present invention is an improvement upon the apparatus described in that patent. Such units have a fan located over the evaporator coils for drawing air from the container and passing it over the evaporator coils to cool the air before passing the air back into the container.

The present invention provides a temperature control unit which uses hydraulic medium for driving motors for fans for the evaporator coils and the condenser coils and utilizing the hydraulic medium to transfer waste heat in the unit to places in which the heat can be usefully employed.

According to the invention there is provided a temperature control unit comprising a refrigeration circuit having a compressor, condenser coils, evaporator coils and interconnected conduit means therefore forming together a closed circuit. Hydraulic motors for fans for the condenser coils and the evaporator coils and a hydraulic fluid pump and hydraulic fluid reservoir are interconnected by first hydraulic conduit means to form a closed hydraulic circuit. In the temperature control unit there is provided also heating means which heating means have heating coils through which hydraulic fluid can pass, a switch valve in the first hydraulic conduit means connecting the motors to the reservoir and second hydraulic conduit means interconnecting the switch valve, the heating coils and the reservoir. With the aforementioned construction operation of the switch valve can pass exhaust fluid from the closed hydraulic circuit into the heating coils.

Preferably the control unit also comprises heat storage means for storing waste heat occurring in the unit and the second hydraulic conduit means pass through the heat storage means for the transfer of heat to the exhaust hydraulic medium from the closed hydraulic circuit.

The heating coils may be used to defrost the evaporator coils or to provide heat in the container when the temperature within the container falls below the reice quired temperature range, or in humidity control of the air in the container.

An embodiment of the invention will now be described by Way of example with reference to the accompanying drawings in which FIG. 1 is a front elevation of a temperature control control unit embodying the invention;

FIG. 2 is a side elevation of the invention of FIG. 1;

FIG. 3 is a schematic diagram of the refrigeration circuit of the unit of FIG. 1;

FIG. 4 is a schematic diagram of the hydraulic circuit of the unit of FIG. 1; and

FIG. 5 is a schematic diagram of the electrical circuit of the unit of FIG. 1.

Referring to FIGS. -1 and 2, the temperature control unit 1 is mounted in frame members 2 and is particularly adapted for mounting in one wall of a transport container (not shown) adapted for the shipment of cargo by road, rail or sea. However, it is to be understood that the unit can be used for any temperature control purpose at any desired location.

Within the frame members 2 are walls 3 which separate a portion of the unit from the remainder of the unit. Located within the walls 3 is an evaporator 4 and a drain pan 5. In an outer wall of the unit defining said portion is an inlet duct 6a for air from the container and an outlet duct 6b for air flowing to the container.

In the remainder of the unit there is located a diesel engine 7 which drives a compressor 8 for the refrigerant by means of an electromagnetic clutch 9 and drives a gear pump 10, through a gear train, for supplying hydraulic fluid under pressure. Located above the diesel engine 7 is a condenser 12. In an outside wall of the unit adapted to be exposed to the atmosphere there is an inlet duct 11a for ambient air and an outlet duct 11b is located adjacent the diesel engine. Also in the said other part of the container is located a battery 32, a hydraulic fluid reservoir 24 and an electrical control panel 60.

The evaporator 4 has a fan 13 driven by a hydraulic motor 14. The fan and motor are located above the evaporator coils in a position to draw air through the inlet duct 6a. The evaporator coils 4a in the refrigerant circuit as will be described and heating coils 31 located above and below the evaporator coils 411 but in the same structural unit. This structural unit has heat conducting fins which are common to both coils 4a and coils 31. In the drain pan 5 is located a heating coil 30 which is in series with the heating coils 31. The condenser 12 has thereabove a fan 15 for passing air over the coils 12a '(FIG. 3) of the condenser and a hydraulic motor 16 for driving the fan 15. The fan 15 draws air in through the duct 11a and passes the air over the condenser coils and over the engine 7 to cool the engine. Exhaust air from the unit passes back into the atmopshere through outlet duct 11b. The duct 11b is made somewhat smaller than the duct 11a so that pressure tends to build up within the unit 1. Thus although the engine is adequately cooled the other components within the temperature control unit are surrounded by air at a greater pressure than the ambient atmospheric air which precludes the entry of dirt and moisture into the unit.

The pump 10 is a constant output pump and each of the motors 14 and 16 is so constructed that each takes half the supply from the pump.

The hydraulic motors 14 and 16, the pump 10, and the heating coils 30 and 31 are interconnected by conduit means to form a hydraulic circuit which will be described in detail hereinafter. Similarly, the evaporator coils 4a, the condenser coils 12a, and the compressor 8 are inter- 3 connected by conduits to form a refrigeration circuit which will be discussed in detail hereinafter. Also, the battery 32 supplies current to not only the engine 7 but an electrical control circuit which also will be discusssed and described later.

FIG. 3 shows the refrigeration circuit used in the apparatus of FIGS. 1 and 2. The refrigeration circuit comprises the compressor 8 which compresses the refrigerant and circulates it through the condenser coils 12a, a filter drier 17, a heat exchanger 18, evaporator coils 4a, and back through the heat exchanger 18 to the compressor 8. A thermostatic expansion valve 22 is located at the en trance to the evaporator coils 4a and relief valve 23 is located at the entrance to the condenser coils 12a to control the operation of the circuit. Also in the circuit is a liquid moisture indicator 21. A defrost control 19 has pressure-sensitive elements 19a and 19b for determining static pressure drop across the evaporator coils 4a when fan 13 is operating and a temperature-sensitive element 19c for measuring the temperature in the evaporator coils. The sensing elements 19a and 19b determine when defrosting of the evaporator coils 4a is required and the sensing element 19c determines when defrosting has been completed. A temperature recorder 58 has a sensitive element 58a located adjacent the evaporator coils and a fan delay thermostat 20 has a sensitive element 20a also located adjacent the evaporator fan coils.

FIG. 4 illustrates schematically the hydraulic circuit of the apparatus of FIGS. 1 and 2. The hydraulic pump 10 is continuously driven by engine 7 and supplies pressurized fluid to evaporator fan motor 14 and condenser fan motor 16, and the exhaust fluid from the motors returns to the reservoir 24, by way of first conduit means comprising common supply conduit 40, evaporator fan motor supply conduit 41, condenser fan supply conduit 42, condenser fan return conduit 43, evaporator fan return conduit 44 and common return conduit 45. A shut-off valve 26 is located in conduit 41. A relief valve 27 in common supply conduit 40 is connected to reservoir 24 by a conduit 46. A shock relief valve 47 is located in conduit 41 and is connected to conduit 45 by conduit 48.

Conduit 45 terminates in a switch valve 28 which is operable to direct fluid either to the reservoir 24 along conduit 49 or to heater coils 31 and to drain pan heating coils 30 along a conduit 50.

As noted above in connection with FIGS. 1 and 2, the heater coils 31 are located above and below but in the same structural unit as the evaporator coils 4a. The drain pan coils are located in the bottom of the drain pan and serve to ensure that any water falling from the evaporator coils is removed from the unit.

Conduit 50 passes through a heat bank 29 which comprises a container 51 filled with wax 52 having a high latent heat factor and a fusion point substantially above that of water. Exhaust gases from engine 7 are directed through the container 51 by duct 53. Return fluid from coils 30 and 31 is led through a conduit 54 to the reservoir 24.

Needle valves 60 in conduits 43 and 44 are adjustable to control the maximum speed of motors 14 and 16.

FIG. shows schematically the electrical circuit of the unit described above. It comprises, to the left of the chain dotted line A-A, the electrical connections for the engine 7 and, to the right of the line AA, the temperature control circuit. The engine circuit comprises the battery 32, a starter motor 55 having a start switch 33, a key switch 34, regulator 35 and generator 36.

The temperature control circuit has a master switch 56 and warning lamp 57 connected across the terminals of the battery 32. In parallel with the lamp 57 is a circuit comprising the defrost control 19, the fan delay thermostat 20, temperature recorder 58, solenoid 28a for operating the switch valve 28, an electrical connection for the electromagnetic clutch 9 for the compressor 8, and a solenoid 26a for controlling the shut-ofi valve 26.

The defrost control 19 has a switch element 19d which is operable by the sensing elements 19a and 19b to transfer current from the circuit to the solenoid 26a to the circuit to the solenoid 28a, i.e. from the position shown in solid line in FIG. 5 to the position shown in dotted line in FIG. 5. Temperature-sensitive element acts on switch element 19a to prevent current passing to the solenoid 26a until such time as the evaporator coils are at a predetermined low temperature. A manual override 19 is provided for actuation of the solenoid valve 28a independently of the defrost control system.

The temperature control unit 58 has switch elements 58b and 580 operable respectively on the solenoid 26a and the clutch 9 and upon the solenoid 28a. The con tact points of the elements 58b and 580 are adjustable to determine a temperature range outside which the elements change the circuit configuration.

The fan delay thermostat 20 has a switch element 20b located in the circuit between the defrost control 19 and the solenoid 26a to prevent actuation of the solenoid 26a until such time as the evaporator coils have reached a certain predetermined low temperature. A manual override 20c is provided in parallel with the thermostat switch element 20b.

In operation of the temperature control unit described above and with a demand for cooling with the cargo container being above the predetermined temperature range, the electrical circuit is in the position shown in solid lines in FIG. 5. In this circuit configuration the electromagnetic clutch 9 is engaged and the compressor 8 is driven by the engine 7. The compressor 8 drives refrigerant around the refrigerant circuit and through the condenser and evaporator coils. Current passes through the circuit to the solenoid 26a to hold the shut-oh valve 26 in open position so that hydraulic fluid is pumped from the gear pump 10 to both the evaporator fan motor 14 and the condenser fan motor 16. No current is passing through the solenoid switch 28a and the switch valve is held in a position in which exhaust fluid from the motors 14 and 16 is directed to the reservoir 24. Thus, it will be seen that condenser fan 15 is in operation to pass cooling air over the condenser coils and the engine 7 and the evaporator fan 13 is in operation to pass air from the container over the coil evaporator coils and back into the container to cool the container.

During the cooling of the air, moisture in the container air tends to freeze out on the evaporator coils. This reduces the flow of air across the evaporator coils and when the pressure-sensitive elements 19a and 19b detect that the pressure drop due to the flow of air is less than a predetermined amount, the switch element 19d switches over to operate the defrost cycle. When the element 19d switches to the position shown in dotted line in FIG. 5, no current passes to the solenoid valve 26a and the shutoff valve 26 closes to stop the evaporator fan motor 14. At the same time, current is passed directly to the solenoid 2811 which actuates the switch valve 28 to pass exhaust fluid from the motor 16 into the conduit 50 and the heating coils 30 and 31. Operation of the switch element 19d also stops current flowing through the temperature recorder and thus through the electromagnetic clutch 9. The compressor is thereby disconnected from the engine and the refrigeration circuit ceases to function. Thus, in the circuit configuration during defrosting, the condenser fan is still operating to pass cooling air over the engine 7 but no air is being passed around the container. During the cooling cycle exhaust gases from the engine 7 have been passed through the duct 53 and the heat has been transferred to the wax 52 in the container 51 which melts the Wax and stores heat for use during the defrosting cycle. Thus, as exhaust fluid from the motor 16 is passed through the heat bank, heat is removed therefrom and passed to the coils 30 and 31. The drain pan coil 30 is first heated to ensure that any water dropping on to the drain pan during defrosting is not refrozen. During defrosting and as heat is removed from the heat bank, the wax comes to the temperature at which it fuses. At this point a great deal of latent heat is liberated by the wax and this is the reason for using a material having a fusion point above that of water.

When the air in the container has been cooled below the predetermined maximum temperature in the temperature range specified, the element 58b is acted upon by the sensitive element 58a to open the contact between the switch 58b and the electromagnetic clutch 9. This stops the compressor and stops the flow of refrigerant around the cycle. However, the solenoid 26a remains activated and the valve 26 open so that the evaporator fan continues to pass air around the container.

Where the ambient atmospheric temperature is below the minimum temperature in the predetermined temperature range for the air in the container, from time to time heating of the air in the container will be required. To achieve this the temperature-sensitive element 58a acts on the switch elements 58b and 58c to deactivate the clutch 9 and to move the switch element 580 to the position shown in broken lines in FIG. 5. In this position current is passed from the temperature recorder 58 to the solenoid 28a to activate the switch valve 28 to pass exhaust fluid from the motor 16 and 14 through the heat bank 29. The solenoid 26a remains activated as current passes through the switch element 20b from the defrosting circuit 19. Should there be a demand for heat during a defrosting cycle, then it will be seen that the switch element 58b can take the position shown in broken lines in FIG. 5 whereupon current is transferred through the switch elements 58c and 58b to the solenoid 26a to reactivate the fan 13 to pass air heated by the coils 30 and 31 through the container.

In the embodiment described heat storage means have been included to make use of waste heat from the internal combustion engine. In some uses the primary motive power source may be an electric motor and the condenser fan may not be required to provide cooling for the motor. If, then, needle valves 60 can also function to shut off flow through motors 14 and 16, the energy stored in the pressurized hydraulic medium from pump can be dissipated into heat in the medium at shock relief valve 47 which is set at a lower release pressure than valve 27. The heated medium can then be supplied through conduit 48 to switch valve 28 and coils 30 and 31. The characteristics of the circuit may then be such as to avoid the need for an external heat supply such as the heat bank 29.

The circuit according to the invention may also be used to control the humidity in the container. As explained above, during cooling of the air, moisture in the air freezes out on the evaporator coils. This is because on cooling the air becomes saturated. It may be that the cargo being carried requires that the relative humidity of the air be less than 100 percent. It is then necessary to reheat the air to reduce the relative humidity. This can be readily achieved according to the present invention by providing an additional set of coils (shown at 70) downstream of the evaporator coils 4a and connecting these coils through the heat bank 29 to the switch valve 28, which is provided with an additional position 71 to direct exhaust fluid from the motors 14 and 16 to the additional set of coils. Then'a humidity sensor can be provided in the container (not shown) which can be connected into the electrical circuit to actuate the switch valve to direct medium through the heat bank and into the additional set of coils when the humidity rises above the required value.

What I claim is:

1. A temperature control unit comprising a refrigeration circuit having a compressor, condenser coils, evaporator coils and interconnecting conduit means therefor forming a closed circuit, a fan for the condenser coils and a motor therefor, a fan for the evaporator fan and a motor therefor, a hydraulic fluid pump and hydraulic fluid reservoir, first conduit means interconnecting said pump, said motors, and said reservoir to form a hydraulic circuit, and heating means, said heating means comprising heating coils through which hydraulic fluid can pass, a switch valve in the first conduit means connecting the said motors to the said reservoir, and second conduit means interconnecting said switch valve, said heating coils and said resenvoir, whereby on operation of said switch valve, exhaust fluid from said hydraulic circuit is passed through said heating coils.

2. A temperature control unit according to claim 1 further comprising an internal combustion engine for driving said pump and said compresser, heat storage means, duct means for conducting hot exhaust gases from said engine through said heat storage means for heat transfer thereinto, at least a portion of the second conduit means for supplying hydraulic fluid to said heating coils extending into said heat storage means for the trans fer of heat to hydraulic fluid in the second conduit means.

3. A temperature control unit according to claim 2 wherein said heat storage means comprises a container having therein a wax having a high latent heat factor and a fusion point substantially above that of water, and said duct means and said portion of said second conduit means passing through said wax.

4. A temperature control unit according to claim 2 wherein said engine drives said pump through a gear train and said compressor through a clutch means.

5. A temperature control unit according to claim 1 wherein said pump is a constant output pump, said motors each take substantially half the supply from the pump, a shut-off valve means for the evaporator motor is provided, and relief valve means is provided in the conduit means between the pump and the shut-olf valve, whereby said evaporator fan motor may be stopped independently of said condenser fan motor.

6. A temperature control unit according to claim 1 wherein the heating coils are located adjacent to the evaporator coils.

7. A temperature control unit according to claim 6 wherein the heating coils and evaporator coils are in a common structure, said structure comprising two sets of heating coils located one set on either side of a set of evaporator coils and the heating and evaporator coils have a common set of outwardly extending heat conducting fins.

8. A temperature control unit according to claim 6, which is used for humidity control and in which a set of heating coils are located in a position spaced apart down stream from the evaporator coils, whereby air leaving the evaporator coils may be heated to reduce its relative humidity.

9. A temperature control unit according to claim 7 further comprising defrost sensing means for determining the effective state of the evaporator coils.

10. A temperature control unit according to claim 9 further comprising an electrical control circuit having a defrost control switch adapted to be actuated by the defrost sensing means, electrical valve actuating means for the switch valve and for a shut-off valve in the first conduit means supplying the evaporator fan motor, and electrically operated compressor control means, on actuation of the defrost control switch on a call for a defrost cycle from the defrosting sensing means, the circuit reacting to close the shut-off valve to stop the evaporator fan, to stop the compressor, and to actuate the switch valve to pass hydraulic fluid around the heating coils.

11. A temperature control unit according to claim 10, wherein, when defrosting is complete, the defrost sensing means actuates the defrost control switch and the electrical circuit reacts to activate the compressor and to operate the switch valve to stop flow of hydraulic fluid through the heating coils, there being provided in the circuit evaporator fan delay means to prevent opening of the shut-off valve until the temperature of the evaporator coils reaches a predetermined value.

12. A temperature control unit according to claim 6 further comprising temperature sensing means for determining the temperature of the air in the container.

13. A temperature control unit according to claim 12 comprising an electrical control circuit having a temperature recording means in operative connection with the temperature sensing means, electrical valve actuating means for the switch valve and electrically operated compressor control means, said temperature recording means having switch means in said circuit operable by the recording means above and below a predetermined container air temperature range, said switch means operable below said temperature range on said circuit to stop the compressor and to actuate the switch valve to pass hydraulic fluid through the heating coils, and said switch means operable above said temperature range to actuate the compressor and to actuate the switch valve to stop the flow of hydraulic fluid through the heating coils.

References Cited UNITED STATES PATENTS ROBERT A. OLEARY, Primary Examiner C. SUKALO, Assistant Examiner US. Cl. X.R.

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