US3722230A - Ship refrigeration - Google Patents

Abstract

A ship refrigeration system permits evaporators in different ship cargo compartments being held at different refrigeration temperatures though the respective evaporators are fed refrigerant from a common source, and control means accessible at a common control center are used for modulating the refrigerant pressures in the evaporators in separate compartments of the ship independently depending upon the cooling load demands in the separate compartments.

Description

United States Patent 1191 Scott et al. Mar. 27, 1973 [5 SHIP REFRIGERATION 2,291,503 7 1942 Persons ..62/217 [75] Inventors: James Scott, Atkinson, NH; John 3,449,923 ls 1969 Hansen et 81.... ..62 217 S McDowell Jr Flushin N Y 1,986,249 /1935 Buehler, Jr ..62/200 1 2,161,312 6 1939 Pritchard ..62/217 X 73 Assigneez United Brands Company, Boston, 3,189,041 6/1965 Hansen ..62/217 X Mass- FOREIGN PATENTS OR APPLICATIONS [22] Wed: 1970 871,231 6/1961 Great Britain ..62/240 [21] Appl. No.: 96,882

Primary Examiner-William F. ODea Assistant Examiner-Peter D. Ferguson [52] US. Cl. ..62/202,2 Atmmey Row]and v. Patrick [51 Int. Cl. ..B63b 25/26 58 Field of Search...62/200, 217, 240, 512, DIG. 2; [57] ABS-IMCT [56] References Cited UNITED STATES PATENTS 1,698,031 1/1929 Smoot 2.36/85 2,371,428 3/1945 De Giers et 236/86 3,365,131 1/1968 Zoludow 236/86 3,371,864 3/1968 Daly et al. ..236/86 2,315,379 3/1943 Robson "52/240 X 1,050,894 l/l913 Williams et a]. ..62/217 X A ship refrigeration system permits evaporator-s in different ship cargo compartments being held at different refrigeration temperatures though the respective evaporators are fed refrigerant from a common source, and control means accessible at a common control center are used for modulating the refrigerant pressures in the evaporators in separate compartments of the ship independently depending upon the cooling load demands in the separate compartments.

2 Claims, 3 Drawing Figures SHIP REFRIGERATION This invention relates to commercial refrigeration and more particularly to a refrigeration system which is better adapted for shipboard installation than any heretofore devised.

Marine carriers are regularly confronted with carrying mixed cargoes. Some of these cargoes often require different refrigeration temperatures than other cargo to be transported on the same voyage. In such cases it may be desirable to hold one compartment at, say a temperature above 32 F while holding another below F or at some other differential temperature. Refrigerated ships with liquid refrigerant recirculation systems thus have had independent refrigerating systems for different compartments so that each system could be set to handle the particular cargo carried in the compartment served by it.

A specific object of the present invention is, in a multicompartment ship, to provide a capability for maintaining temperature differentials among different compartments, while avoiding duplication of equipment, thereby affording savings in initial and maintenance costs. This invention also makes it feasible to locate all manual setting and controlling devices at a common station, as in an engine room, which in turn permits a reduction in manned stations and in crew numbers. The controlling device operated from the common station also provides for modulation of the pressures in the.

evaporators in different compartments according to the cooling load demands.

Such objects are accomplished in accordance with this invention by utilizing any of the common refrigerants such as R22, R505, R12 or R717 in a liquid recirculation refrigeration system which has separate evaporators for different compartments, with the evaporators being connected in parallel between a common feed line and a common return line to other conventional components of a single liquid recirculation refrigeration system including a compressor, a condenser, a refrigerant accumulator, a refrigerant metering device and a pump.

A pressure regulator is placed downstream from the evaporator or evaporators in the return line and, in order to permit the system to operate with the pressure regulators set for substantially different values, check valves are interposed upstream of each evaporator so that the temperatures of the refrigerant in the evaporators may be maintained at widely different desired levels above the level of the refrigerant temperature in the accumulator.

The air temperature at each evaporator can therefore be accurately controlled without disturbing the pressure or temperature in other evaporators con nected in the same refrigerant circuit.

Such a system may be more readily understood by reference to the accompanying drawings wherein:

FIG. 1 is a diagrammatic representation of a ship having an engine room and several holds;

FIG. 2 is a schematic diagram of a refrigeration system; and

FIG. 3 is a schematic diagram of a valve control system.

Referring to H6. 2, represents an accumulator interposed in a return line 12 leading to a compressor 14 which discharges into a condenser 16 from which liquid is returned through a high pressure float valve 18 to the accumulator 10. A liquid pump'20 in a feed line 22 leads to two parallel lines 24 and 26 feeding two evaporators connected in parallel to common return line 12.

Each evaporator designated as 30 in line 24 and as 32 in line 26 has a pressure regulating valve downstream of the evaporator, the valve in line 24 being designated 40 and the valve in line 26 being designated 42. Upstream from each evaporator in lines 24 and 26 there is a check valve 50 and 52, respectively, preceded by a throttle valve 60 and 61 respectively.

As can be seen, if the evaporator pressure regulators are set for the same pressure the system can be operated to feed a constant quantity'of refrigerant to each evaporator regardless of the load in each compartment with the quantity of liquid refrigerant circulated always being more than can be evaporated and the unevaporated liquid returning to the accumulator 10 for recirculation.

The presence of the check valves however permits setting the evaporator pressure regulators at different settings so that the pressure in each of the evaporators corresponds to the refrigerant temperature required to maintain a given temperature in an airstream passing over that evaporator.

For example, if a system is set up to operate with the refrigerant at 20 F and 10 psi. in the accumulator 10 with the compressor maintaining the pressure in the accumulator at 10 p.s.i., the regulator 40 in parallel line 24 may be set for a pressure of 13 p.s.i. while the other regulator 42 can be set for example for a pressure of 48 psi. with the result that the refrigerant in evaporator 30 will cool to l5 F and that in evaporator 32 to 24 F, which temperatures are suitablefor maintaining the cargo spaces at 10" F and 35 F respectively.

Because of the presence of the check valve 52 the pressure of the refrigerant in evaporator 32 may be held above the pressure in evaporator 30. Or, of course, the settings may be reversed because of the presence of check valve 50.

The pressure regulators respond to sensors placed in the air streams so that when the air temperature rises above the sensor temperature setting, the suction pressure in the refrigeration system is lowered, and when the air temperature falls below the sensor temperature setting, the pressure is raised, thereby maintaining constant air temperature and varying the refrigerant pressure within the evaporator.

The rest of the closed system constitutes no part of the invention, however, it is described herewith for clarification. It will be understood that there is'twophase flow of refrigerant in the return pipe 12. The I liquid returning from the evaporators falls to the bottom of accumulator 10 for recirculation, while the gas returning from the evaporators separates in the accumulator and is returned in suction line 13 to the compressor 14 where it is compressed to the condensing pressure and flows to the condenser 16 where it is condensed to high pressure liquid by heat exchange with a water coolant, for example sea water in the case. of a ship.

A metering device in the form ofa high pressure float valve 18 drains the liquid from the condenser 16 and meters it to, and at the pressure in, the accumulator l0.

The system is actuated and the capacity controlled by operating the compressor 14 responsive to a pressure sensor in the suction line 13.

The pressure regulator valves 40 and 42 are responsive to temperature sensors 62 and 63 in the air streams actuating a centrally located pneumatic controller 70 shown in FIG. 3.

With 100 p.s.i. pneumatic supply, the controller preferably operates on the normal maximum pressure of 20 p.s.i. obtained by passing through a pressure reducing valve 72 (FIG. 3).

The output signal of the controller at 74 supplies a modulating air regulating valve 76 to provide to 15 p.s.i. pressure plus the pre-set air-regulating valve pressure of 0-100 p.s.i. and the spring pressure on the evaporator pressure regulating valve 42. Combinations of the above will automatically regulate the evaporator pressure to maintain any space temperature between 1 0 F and 60 F.

It will be understood that one of the systems as shownin FIG. 3 is provided for each compartment in the ship. In the case of one regulating valve, taken as an example, if a space temperature of 35 F in its compartment is desired, the system may be designed so as to provide a 24 F minimum evaporator temperature. This corresponds in the case [(-22 refrigerant to a saturation pressure of 48 p.s.i. The pressure regulating valve springs are set at p.s.i. Therefore valve 76 should be set at 48 p.s.i. minus 10 p.s.i. or 38 p.s.i.

If temperature setting switch 78 is then set at 35 F, 35 F air temperature will then be maintained as the evaporator pressure modulates to give an evaporator temperature running between 24 F and 32 F depending upon the cooling load in the compartment space.

- Temperature setting switches 78 and 79 for different compartments A and C are shown in FIG. 1 located ata common control center remote from the compartments, for example in the engine room. They act independently to set valves 40 and 42 to maintain evaporator pressures at selected minimums. The sensors 62 and 63 then act through the controls 70 and 71, and

separate valves 76 to cause the regulating valves 40 and 42 to modulate the pressures in the evaporators so that they remain at or near their set minimum values while cooling load demands are high but automatically rise as cooling load demands decrease as the space temperatures in the compartments gradually drop until the pressures have risen to provide temperatures in the evaporators corresponding to the highest temperatures which will still maintain cargoes in the compartments at the respective desired low temperatures.

The pressure, and hence temperature, in each evaporator is maintained by its check valve and is independent of the temperature in the other evaporators in the system.

What is claimed is:

1. A refrigeration ship adapted to transport food products such as bananas requiring a storage temperature of from about 52 F to 60 F and other food products which require a storage temperature of about -10 F and temperatures inbetween --l0 F to 60 F in cargo compartments comprising a liquid recirculation refrigeration system for maintaining said compartments at the same or different refrigeration temperatures from refrigerant fed from a common source, said system having (an) a low pressure accumulator for holding a body of liquid refrigerant under relatively low pressure at a temperature lower than the lowest space temperature required, a feed line leading from said accumulator, a pump in said feed line for raising the pressure of the liquid refrigerant, a return line leading to said accumulator, a compressor and condenser communicating with said accumulator, evaporators connected in parallel between said feed line and said return line and located in different compartments of said ship at elevations above or below said low pressure accumulator, a pressure regulator valve in each parallel line downstream of its evaporator, and a check valve in each parallel line upstream of its evaporator, said regulating valves being set to maintain the pressure in said evaporators at different levels corresponding to temperatures above the temperature of the refrigerant in said accumulator.

2. A refrigeration ship as set forth in claim 1 further including means located at a common control center remote from each said pressure regulator valve for adjustably controlling the pressure of fluid flowing therethrough.

Claims (2)

1. A refrigeration ship adapted to transport food products such as bananas requiring a storage temperature of from about 52* F to 60* F and other food products which require a storage temperature of about -10* F and temperatures inbetween -10* F to 60* F in cargo compartments comprising a liquid recirculation refrigeration system for maintaining said compartments at the same or different refrigeration temperatures from refrigerant fed from a common source, said system having (an) a low pressure accumulator for holding a body of liquid refrigerant under relatively low pressure at a temperature lower than the lowest space temperature required, a feed line leading from said accumulator, a pump in said feed line for raising the pressure of the liquid refrigerant, a return line leading to said accumulator, a compressor and condenser communicating with said accumulator, evaporators connected in parallel between said feed line and said return line and located in different compartments of said ship at elevations above or below said low pressure accumulator, a pressure regulator valve in each parallel line downstream of its evaporator, and a check valve in each parallel line upstream of its evaporator, said regulating valves being set to maintain the pressure in said evaporators at different levels corresponding to temperatures above the temperature of the refrigerant in said accumulator.

2. A refrigeration ship as set forth in claim 1 further including means located at a common control center remote from each said pressure regulator valve for adjustably controlling the pressure of fluid flowing therethrough.

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