MULTI-EVAPORATOR SEQUENCING APPARATUS AND METHOD

A refrigerant system includes a condenser and a plurality of evaporators each connected to the condenser. Each of the plurality of evaporators receives fluid from the condenser in a harvest mode, and at least two of the plurality of evaporators are in a harvest mode at different times.

BACKGROUND OF THE DISCLOSURE

1. Field of the Disclosure

The present disclosure relates generally to an apparatus and method for cooling with multiple evaporators. More particularly, the present disclosure relates to an apparatus and method for sequencing a harvest mode and a freezing mode of each of a plurality of evaporators.

2. Description of Related Art

Conventional commercial batch-style ice making machines bring in a certain amount of potable water, freeze a portion of that water into ice, harvest that ice, then repeat the process. These machines have one or more evaporators for the freezing and harvesting of ice. For example, referring toFIG. 1, ice making assembly30has an ice making machine33that makes ice and an ice bin31that stores ice.

FIGS. 2 and 3illustrate schematically a water/ice system of ice making assembly30, but does not show the ice bin31or reservoir. A water supply1provides source water. Attached lines control and direct the flow of water from the water supply to flow into a water sump3. The sump is equipped with a level controller2, a solenoid dump valve9, a drain line10, and is connected and supplies a water supply to the suction side of the circulating pump4. Pump4circulates water from sump3to the distributor7, where the water is directed over an evaporator plate6. Evaporator plate has walls6a,6b,6c,6dthat form ice having a shape, e.g., cubes.

The water from the distributor7is directed across the evaporator plate6and, if not frozen to form ice on a first pass, is collected by the water curtain5. This collected water is allowed to flow down the water curtain into the water sump or water reservoir3, where it is collected and again circulated by the circulating pump4to the distributor7and recycled across evaporator plate6during the freezing cycle. Once the ice forming on the evaporator plate6has reached a certain thickness, the water flowing over the surface of that frozen ice product reaches contact with the ice thickness probe8, which signals the controller to stop the freeze mode and begin the harvest mode.

FIG. 4shows an example of ice making assembly30that has two evaporator plates6. Each of evaporator plates6is connected to a refrigerant system having multiple evaporators, one for each evaporator plate6, which operates in the freeze mode and the harvest mode.

Referring toFIG. 5, an example of a refrigerant system100that has multiple evaporators102is shown. Refrigerant system100has four evaporators104,106,108,110. Evaporators102are each in thermal contact with an evaporator plate to heat and cool the evaporator plate. For example, one of evaporator plates6may be heated and cooled by evaporator104and the other of evaporator plates6may be cooled by evaporator106shown inFIGS. 2-4. Refrigerant system100comprises a condenser111, evaporators104,106,108,110, a compressor114, refrigerant supply line120, a drier121, a receiver122, harvest solenoid valves123, and expansion valves113for each of evaporators102.

Referring toFIG. 6, in the freeze mode, each of evaporators104,106,108,110inlet has low-pressure liquid132that expands, absorbs heat, and evaporates, changing to a low-pressure vapor134in evaporator serpentine112. Compressor114pumps low-pressure vapor134from inlets of each of evaporators104,106,108,110to condenser111increasing the pressure forming high pressure vapor136at condenser111. In condenser111, heat is removed from high pressure vapor136, which then condenses and becomes a high-pressure liquid138. This high-pressure liquid138drains from condenser111into receiver tank122to provide a buffer for refrigerant as demand varies. One of expansion devices113is between condenser111and each of evaporators104,106,108,110. Immediately preceding each of expansion devices113is drier121, which prevents plugging of the valve or tube by retaining scale, dirt, and moisture. As high-pressure liquid138enters the evaporators104,106,108,110, it is subjected to a much lower pressure due to the suction of compressor114and a pressure drop across expansion devices113. Thus, the refrigerant tends to expand and evaporate. In order to evaporate, the liquid must absorb heat from the air passing over evaporators104,106,108,110forming low pressure liquid132. Harvest solenoid valves123are closed during the freeze mode.

Referring toFIG. 7, when the ice making system goes into its harvest mode, each of open expansion devices113are closed and each of closed harvest solenoid valves123are opened allowing high pressure vapor136in compressor114to flow through refrigerant supply line120into each of evaporators104,106,108,110. High pressure vapor136flows toward each of evaporators104,106,108,110through each of harvest solenoid valves123lowering the pressure to form low-pressure vapor134. Low-pressure vapor134flows through each of evaporators104,106,108,110lowering pressure further forming low pressure liquid132. Low pressure liquid132flows from each of evaporators104,106,108,110to compressor114.

Each of evaporators102are cooled by boiling refrigerant in evaporator serpentine112while water is circulated over evaporator plates6to freeze ice when the machine is in “freeze mode”. Evaporators102are warmed by routing high pressure vapor136that is at a higher temperature than ice that is formed on evaporator plates6through the evaporator serpentine112to melt ice and allow gravity to pull an ice slab off evaporator plates6when the machine is in “harvest mode”. The use of multiple evaporators102in these conventional machines is strictly to add more evaporator surface area than could be fit in the given machine size with only one large evaporator. All the evaporators102in the system are synchronized in their freezing modes and harvesting modes so that evaporators104,106,108,110all operate in the same mode, freezing mode or harvesting mode, all at the same time.

The synchronized nature of all evaporators102in a conventional multi-evaporator machine used in refrigerant system100results in a maximum heat load condition from all evaporators102happening at the same time, as well as a minimum heat load condition from all evaporators102happening at the same time. This leads to large variations in operating conditions for compressor114, from very high discharge pressure early in the “freeze mode” to very low suction pressure late in the “freeze mode.” These times of high discharge pressure or low suction pressure result in the compressor running at less efficient points than the average load condition due to reduced refrigerant throughput.

Accordingly, it has been determined by the present disclosure, there is a need for spreading out the refrigeration load of a refrigeration system throughout the freeze mode (load leveling) to best utilize cooling capacity of the refrigerant system and to maximize its efficiency.

SUMMARY

A refrigerant system is provided that includes a condenser and a plurality of evaporators each connected to the condenser. Each of the plurality of evaporators receives fluid from the condenser in a harvest mode, and at least two of the plurality of evaporators are in a harvest mode at different times.

The above-described and other advantages and features of the present disclosure will be appreciated and understood by those skilled in the art from the following detailed description, drawings, and appended claims.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring to the drawings and in particular toFIG. 8, an exemplary embodiment of a refrigerant system of the present disclosure is generally referred to by200. Refrigerant system200has a compressor201connected to condenser202. Condenser202is connected to a plurality of evaporators205.FIG. 8has four evaporators: first evaporator205a,second evaporator205b,third evaporator205cand fourth evaporator205d.Additional or fewer evaporators205may be included in refrigerant system200, however, at least two evaporators205are used. Between the connection of condenser202and each of evaporators205is a liquid line valve204. Each of evaporators205is connected to compressor201. Between the connection of compressor201and each of evaporators205is a suction line valve209. Between each of evaporators205are a check valve206, which is allows flow of fluid only in a single direction, and an expansion valve208. An expansion valve header207is a conduit that connects each of check valves206and expansion valves208to one another. A liquid line header203is a conduit that connects each of liquid line valves204to one another. A suction line header210is a conduit that connects each of suction line valves209to one another. One or more conduits may connect compressor201condenser202, liquid line header203, liquid line valves204, evaporators205, check valves206, expansion valve header207, expansion valves208, suction line valves209and suction line header210to one another to circulate refrigerant therein. Refrigerant may include R404A, R410A, R32, or the like. Refrigerant system200has liquid line valves204of first evaporator205a,a second evaporator205b,and a third evaporator205cin a closed position and suction line valves209of first evaporator205a,a second evaporator205b,and a third evaporator205cin an open position so that first evaporator205a,a second evaporator205b,and a third evaporator205care in a freeze mode. Refrigerant system200has liquid line valve204of fourth evaporator205din an open position and suction line valve209of fourth evaporator205din a closed position so that fourth evaporator205dis in a harvest mode.

Referring toFIG. 9, suction line valve209of first evaporator205ais in a closed position blocking refrigerant from flowing from first evaporator205ato compressor201. Liquid line valve204of first evaporator205ais in an open position allowing refrigerant to flow from condenser202to first evaporator205a. Suction line valves209of second evaporator205b,third evaporator205c,and fourth evaporator205dare in an opened position allowing refrigerant to flow to compressor201from each of second evaporator205b,third evaporator205c, and fourth evaporator205d.Liquid line valves204of second evaporator205b, third evaporator205c,and fourth evaporator205dare in a closed position blocking refrigerant from flowing from condenser202to each of second evaporator205b,third evaporator205c,and fourth evaporator205d.

In operation, low pressure refrigerant vapor234is compressed in compressor201to form high pressure refrigerant vapor236. High pressure refrigerant vapor236flows from compressor201through condenser202to reject heat, condensing high pressure refrigerant vapor236to form high pressure liquid238. High pressure liquid238is routed from condenser202through liquid line header203. High pressure liquid238travels through open liquid line valve204for first evaporator205athat is in a harvest mode. High pressure liquid238travels through first evaporator205athat is in harvest mode. High pressure liquid238travels through check valve206for first evaporator205ain the harvest mode. High pressure liquid238is routed through expansion valve header207, splitting into separate streams for each of second evaporator205b,third evaporator205c,and fourth evaporator205dthat are each in a freeze mode. High pressure liquid238travels through expansion valves208for each of second evaporator205b,third evaporator205c,and fourth evaporator205dforming low pressure liquid232in the freeze mode. Low pressure liquid232travels through second evaporator205b,third evaporator205c,and fourth evaporator205dthat are in freeze mode, evaporating refrigerant from low pressure liquid232forming low pressure vapor234. Low pressure vapor234streams travel through suction line valves209. Low pressure vapor234streams combine in suction line header210. Low pressure vapor234returns to compressor201. This cycle of refrigerant transforming from low pressure vapor234to high pressure refrigerant vapor236to high pressure liquid238to low pressure liquid232and back to low pressure vapor234in refrigerant system200repeats until the harvest mode of first evaporator205aand the freeze mode of second evaporator205b,third evaporator205c,and/or fourth evaporator205dare completed. Freeze and harvest times may be determined by monitoring water level in the water sump, for example, sump3, monitoring suction pressure or temperature, or based on a time value or array of time values of the harvest cycle versus ambient temperatures.

Each of second evaporator205b,third evaporator205c,and fourth evaporator205dare cooled by low pressure liquid232while water is circulated over evaporator plates, e.g., evaporator plates6ofFIG. 4, that are in thermal contact with one of second evaporator205b,third evaporator205c,and fourth evaporator205dto freeze ice in the freeze mode. First evaporator205ais warmed by routing high pressure liquid238that is at a higher temperature than ice that is formed on an evaporator plate, e.g., one of evaporator plates6ofFIG. 4, to melt ice and allow gravity to pull an ice slab off evaporator plate6when in the harvest mode.

First evaporator205ahas a liquid line heat harvest for the harvest mode that is accomplished by routing refrigerant from an outlet of condenser202through first evaporator205awhile the remaining second evaporator205b,third evaporator205c,and fourth evaporator205dare in the freeze mode. After high pressure liquid238exits first evaporator205athat is in harvest mode, a flow of high pressure liquid238is split and routed to expansion devices208for each of the remaining second evaporator205b,third evaporator205c,and fourth evaporator205dthat are in the freeze mode.

Refrigerant system200has a controller214. Controller214has a processor216and a memory218. Memory218stores a program for operation of refrigerant system200that is executed by processor216. After a certain amount of time, refrigerant system200proceeds to harvest second evaporator205band returns first evaporator205previously in the harvest mode into a freeze mode. Controller214is connected to liquid line valves204and suction line valves209. Memory218stores the program for operation of refrigerant system200that is executed by processor216so that controller214can open and close each of liquid line valves204and suction line valves209.

Referring toFIG. 10, suction line valve209of first evaporator205ais moved to an open position allowing refrigerant to flow from first evaporator205ato compressor201. Liquid line valve204of first evaporator205ais moved to a closed position blocking refrigerant to flow from condenser202to first evaporator205a.Suction line valves209of third evaporator205cand fourth evaporator205dare maintained in the opened position allowing refrigerant to flow to compressor201from each of third evaporator205cand fourth evaporator205d. Liquid line valves204of third evaporator205cand fourth evaporator205dare maintained in a closed position blocking refrigerant from flowing from condenser202to each of third evaporator205cand fourth evaporator205d.Suction line valve209of second evaporator205bis moved to a closed position blocking refrigerant from flowing from second evaporator205bto compressor201. Liquid line valve204of second evaporator205bis moved to an open position allowing refrigerant to flow from condenser202to second evaporator205b.

In operation, low pressure refrigerant vapor234is compressed in compressor201to form high pressure refrigerant vapor236. High pressure refrigerant vapor236flows from compressor201through condenser202to reject heat, condensing high pressure refrigerant vapor236to form high pressure liquid238. High pressure liquid238is routed from condenser202through liquid line header203. High pressure liquid238travels through open liquid line valve204for second evaporator205bthat is in a harvest mode. High pressure liquid238travels through second evaporator205bthat is in harvest mode. High pressure liquid238travels through check valve206for second evaporator205bin the harvest mode. High pressure liquid238is routed through expansion valve header207, splitting into separate streams for each of first evaporator205a,third evaporator205c,and fourth evaporator205dthat are each in a freeze mode. High pressure liquid238travels through expansion valves208for each of first evaporator205a,third evaporator205c,and fourth evaporator205dforming low pressure liquid232in the freeze mode. Low pressure liquid232travels through first evaporator205a,third evaporator205c,and fourth evaporator205dthat are in freeze mode, evaporating refrigerant from low pressure liquid232forming low pressure vapor234. Low pressure vapor234streams travel through suction line valves209of first evaporator205a,third evaporator205c,and fourth evaporator205d.Low pressure vapor234streams combine in suction line header210. Low pressure vapor234returns to compressor201. This cycle of refrigerant transforming from low pressure vapor234to high pressure refrigerant vapor236to high pressure liquid238to low pressure liquid232and back to low pressure vapor234in refrigerant system200repeats until the harvest mode of second evaporator205band the freeze mode of first evaporator205a,third evaporator205c,and/or fourth evaporator205dare completed.

Referring toFIG. 11, when the harvest mode of second evaporator205band the freeze mode of third evaporator205care completed, suction line valve209of second evaporator205bis moved to the open position allowing refrigerant to flow from second evaporator205bto compressor201. Liquid line valve204of second evaporator205bis moved to the closed position blocking refrigerant to flow from condenser202to second evaporator205b.Suction line valves209of first evaporator205aand fourth evaporator205dare maintained in the opened position allowing refrigerant to flow to compressor201from each of first evaporator205aand fourth evaporator205d.Liquid line valves204of first evaporator205aand fourth evaporator205dare maintained in a closed position blocking refrigerant from flowing from condenser202to each of first evaporator205aand fourth evaporator205d.Suction line valve209of third evaporator205cis moved to a closed position blocking refrigerant from flowing from third evaporator205cto compressor201. Liquid line valve204of third evaporator205cis moved to an open position allowing refrigerant to flow from condenser202to third evaporator205c.

In operation, low pressure refrigerant vapor234is compressed in compressor201to form high pressure refrigerant vapor236. High pressure refrigerant vapor236flows from compressor201through condenser202to reject heat, condensing high pressure refrigerant vapor236to form high pressure liquid238. High pressure liquid238is routed from condenser202through liquid line header203. High pressure liquid238travels through open liquid line valve204for third evaporator205cthat is in a harvest mode. High pressure liquid238travels through third evaporator205cthat is in harvest mode. High pressure liquid238travels through check valve206for third evaporator205cin the harvest mode. High pressure liquid238is routed through expansion valve header207, splitting into separate streams for each of first evaporator205a, second evaporator205b,and fourth evaporator205dthat are each in a freeze mode. High pressure liquid238travels through expansion valves208for each of first evaporator205a,second evaporator205b,and fourth evaporator205dforming low pressure liquid232in the freeze mode. Low pressure liquid232travels through first evaporator205a,second evaporator205b,and fourth evaporator205dthat are in freeze mode, evaporating refrigerant from low pressure liquid232forming low pressure vapor234. Low pressure vapor234streams travel through suction line valves209of first evaporator205a,second evaporator205b,and fourth evaporator205d.Low pressure vapor234streams combine in suction line header210. Low pressure vapor234returns to compressor201. This cycle of refrigerant transforming from low pressure vapor234to high pressure refrigerant vapor236to high pressure liquid238to low pressure liquid232and back to low pressure vapor234in refrigerant system200repeats until the harvest mode of third evaporator205cand the freeze mode of first evaporator205a,second evaporator205b,and/or fourth evaporator205dare completed.

Referring toFIG. 12, when the harvest mode of third evaporator205cand the freeze mode of fourth evaporator205dare completed, suction line valve209of third evaporator205cis moved to the open position allowing refrigerant to flow from third evaporator205cto compressor201. Liquid line valve204of third evaporator205cis moved to the closed position blocking refrigerant to flow from condenser202to third evaporator205c.Suction line valves209of first evaporator205aand second evaporator205bare maintained in the opened position allowing refrigerant to flow to compressor201from each of first evaporator205aand second evaporator205b.Liquid line valves204first evaporator205aand second evaporator205bare maintained in a closed position blocking refrigerant from flowing from condenser202to each of first evaporator205aand second evaporator205b.Suction line valve209of fourth evaporator205dis moved to a closed position blocking refrigerant from flowing from fourth evaporator205dto compressor201. Liquid line valve204of fourth evaporator205dis moved to an open position allowing refrigerant to flow from condenser202to fourth evaporator205d.

In operation, low pressure refrigerant vapor234is compressed in compressor201to form high pressure refrigerant vapor236. High pressure refrigerant vapor236flows from compressor201through condenser202to reject heat, condensing high pressure refrigerant vapor236to form high pressure liquid238. High pressure liquid238is routed from condenser202through liquid line header203. High pressure liquid238travels through open liquid line valve204for fourth evaporator205dthat is in a harvest mode. High pressure liquid238travels through fourth evaporator205dthat is in harvest mode. High pressure liquid238travels through check valve206for fourth evaporator205din the harvest mode. High pressure liquid238is routed through expansion valve header207, splitting into separate streams for each of first evaporator205a, second evaporator205b,and third evaporator205cthat are each in a freeze mode. High pressure liquid238travels through expansion valves208for each of first evaporator205a,second evaporator205b,and third evaporator205cforming low pressure liquid232in the freeze mode. Low pressure liquid232travels through first evaporator205a,second evaporator205b,and third evaporator205cthat are in freeze mode, evaporating refrigerant from low pressure liquid232forming low pressure vapor234. Low pressure vapor234streams travel through suction line valves209of first evaporator205a,second evaporator205b,and third evaporator205c,Low pressure vapor234streams combine in suction line header210. Low pressure vapor234returns to compressor201. This cycle of refrigerant transforming from low pressure vapor234to high pressure refrigerant vapor236to high pressure liquid238to low pressure liquid232and back to low pressure vapor234in refrigerant system200repeats until the harvest mode of fourth evaporator205dand the freeze mode of first evaporator205a,second evaporator205b,and/or third evaporator205care completed.

Refrigerant system200has a liquid line heat harvest that is accomplished by routing refrigerant from an outlet of condenser202through at least one of first evaporator205a,second evaporator205b,third evaporator205c,and/or fourth evaporator205dwhile the remaining evaporators of first evaporator205a, second evaporator205b,third evaporator205c,and/or fourth evaporator205dare in freeze mode. After high pressure liquid238exits the evaporator currently in harvest mode, a flow of high pressure liquid238is split and routed to expansion devices208for the remaining first evaporator205a,second evaporator205b,third evaporator205c,and/or fourth evaporator205dthat are in freeze mode. After a certain amount of time, refrigerant system200proceeds to harvest another of first evaporator205a,second evaporator205b,third evaporator205c,and/or fourth evaporator205dand returns the evaporator previously in harvest mode back into freeze mode.

Refrigerant system200has at least one of first evaporator205a,second evaporator205b,third evaporator205c,and fourth evaporator205din harvest mode while the remaining evaporators205of first evaporator205a,second evaporator205b,third evaporator205c,and fourth evaporator205dare in freeze mode at all times. More than one evaporator205may be in harvest mode at a time.

Referring toFIG. 13, a method300that can be used with refrigeration system200is shown. Method300begins at step302and proceeds to step304. Step304determines if the refrigerant system in an ice making mode. If the refrigerant system200is not in an ice making mode, then method300repeats step302. If the refrigerant system200is in an ice making mode where ice is made, for example, in an ice making machine30shown inFIG. 4, then evaporators are identified by numbers where n equals the number of evaporators in the refrigerant system, for example, first evaporator205a,second evaporator205b,third evaporator,205cand fourth evaporator205dso that n equal four. Method300proceeds from step306to step308where liquid line valve204of evaporator n, for example, fourth evaporator205d,and suction line valves of the remaining evaporators, for example, first evaporator205a,second evaporator205b,and third evaporator205c,are maintained or opened to an open position, and suction line valve of evaporator n, for example, fourth evaporator205d,and liquid line valves of the remaining evaporators, for example, first evaporator205a,second evaporator205b,and third evaporator205c,are closed or maintained in a closed position so that evaporator n, for example, fourth evaporator205d,is in a harvest mode and the remaining evaporators, for example, first evaporator205a,second evaporator205b,and third evaporator205c,are in freeze mode.

Method300proceeds from step308to step310where it is determined if the harvest mode of evaporator n, for example, fourth evaporator205d,and the freeze mode of one of the remaining evaporators, for example, third evaporator205c,has ended. If the harvest cycle and freeze cycle have not ended, then step310is repeated. If the harvest cycle and freeze cycle have ended, then method200proceeds to step312. In step312it is determined if refrigerant system200is in the ice making mode. If refrigerant system200is not in the ice making mode, then method300ends in step320. If refrigerant system200is in the ice making mode, then method300proceeds to step314where the value of n is changed to n minus one, for example, n was four and will be changed to three. Method300then proceeds to step316where it is determined if n equals zero. If n does not equal zero, for example, n equals three, then method200proceeds to step308, and method200repeats steps308-316, for example, with third evaporator205cin harvest mode and first evaporator205a,second evaporator205b,and fourth evaporator205din freeze mode. If n equals zero, then method200proceeds from step316to step318. If refrigerant system200is not in the ice making mode, then method300ends in step320. If refrigerant system200is in the ice making mode, then method proceeds to step306, and steps306-316are repeated.

Controller214may be coupled to a network, e.g., the Internet. Controller214may include a user interface, processor216, and memory218. Although controller214is represented herein as a standalone device, it is not limited to such, but instead can be coupled to other devices (not shown) via the network. Processor216can be configured of logic circuitry that responds to and executes instructions.

Memory218stores data and instructions for controlling the operation of processor216. Memory218may be implemented in a random access memory (RAM), a hard drive, a read only memory (ROM), or a combination thereof. One component of memory218is a program module220.

Program module220contains instructions for controlling processor216to execute the methods described herein. For example, as a result of execution of program module220, processor216executes method300. The term “module” is used herein to denote a functional operation that may be embodied either as a stand-alone component or as an integrated configuration of a plurality of sub-ordinate components. Thus, program module220may be implemented as a single module or as a plurality of modules that operate in cooperation with one another. Moreover, although program module220is described herein as being installed in memory218, and therefore being implemented in software, it could be implemented in any of hardware (e.g., electronic circuitry), firmware, software, or a combination thereof.

The user interface includes an input device, such as a keyboard or speech recognition subsystem, for enabling a user to communicate information and command selections to processor216. The user interface also includes an output device such as a display or a printer. A cursor control such as a mouse, track-ball, or joy stick, allows the user to manipulate a cursor on the display for communicating additional information and command selections to processor216. The user interface may be provided so that the number of evaporators205included in refrigerant system200may be changed.

This present invention accomplishes the goal of refrigeration load leveling in a multi-evaporator systems by removing the evaporator synchronization that exists in conventional multiple evaporator batch-style ice making machines. Instead, refrigerant system200sequences evaporators205so their maximum and minimum refrigerant loads do not happen at the same time. To do this, the nature of the harvest mode has been changed from the conventional hot gas bypass harvest to a liquid line heat harvest. This change in harvest mechanism allows the system to have one or more evaporators205in harvest mode while the remaining evaporator(s) are in freeze mode. This would not be desirable in systems using hot gas bypass harvest as the evaporator(s) in harvest mode would disrupt the suction pressure of the evaporator(s) in freeze mode.

Refrigerant system200saves energy by sequencing the harvest and freeze modes of evaporators205so that evaporators205are not all in the harvest mode at once or all in the freeze mode at once. This avoids having a maximum heat load condition from all evaporators205happening at the same time, as well as a minimum heat load condition from all evaporators205happening at the same time to avoid large variations in operating conditions for compressor201, from very high discharge pressure early in the freeze mode to very low suction pressure late in the freeze mode, which result in the compressor running at less efficient points than the average load condition. By avoiding large variations in operating conditions for compressor201energy is saved and larger or a greater number of evaporators205may be used relative to a size of compressor201over the prior art. Moreover, refrigerant systems200are limited in size by space needed for condenser202space which relates to a maximum load on a condenser so that avoid large variations in operating conditions also allows larger or a greater number of evaporators205may be used relative to a size of condenser202over the prior art. Furthermore, avoiding large variations in operating conditions will also lead to a greater yield of the amount of ice made using refrigerant system200.