CA2476592A1

CA2476592A1 - Method and apparatus for cooling and dehumidifying air

Info

Publication number: CA2476592A1
Application number: CA002476592A
Authority: CA
Inventors: Marc A. Paradis
Original assignee: Individual
Current assignee: GENEST CLAUDE
Priority date: 2002-02-28
Filing date: 2003-02-26
Publication date: 2003-09-04
Also published as: US20050091993A1; WO2003073028A1; AU2003205483A1

Abstract

A method and an apparatus for rapidly cooling and dehumidifying air within a space. In this method, air to be cooled and dehumidified is forced into a cooling zone including an evaporator (101) having fins (103) forming air channels. The fins and the air channels are preferably substantially vertical.
Air is circulated between the space and the cooling zone in such a manner that the air circulates within the air channels and droplets of condensed water resulting from condensation are evacuated from the cooling zone. One advantage of the above method and apparatus for carrying out the same is that the evaporator can be completely cleaned and sanitized in a few minutes. Since the apparatus allows rapid shedding of any condensation off of the evaporator, freeze-ups never occur. Defrosting is thus eliminated, saving precious time and electrical energy. The above apparatus is particularly adapted for rapidly cooling food.

Description

METHOD AND APPARATUS FOR COOLING AND DEHUMIDIFYING
AIR
Field of the invention The present invention relates to a method for rapidly cooling and dehumidifying air. It also relates to an apparatus for carrying out said method.
Background of the invention The hospitality industry comprises over 300,000 hotels and ~ millions restaurants worldwide. It employs 60 millions people and contributes to 950 billions US$
of the global economy. One of the major challenges it now faces is a growing concern for health and well-being. Indeed, a growing number of consumers want to be given assurances about the quality of the food chain.
This concern is really not surprising, considering the high rate of food-poisoning incidents occurring each year (33 millions in the U.S.A., including 9,000 deaths).

2 0 Governments have thus stepped in and the food transformation industry now finds itself with far more severe regulations for the safe preparation, handling, cooking, conservation and distribution of food. For example, in the United States, meat factories now have to conform to severe standards imposed by HACCP (Hazard Analysis Critical Control Points). The HACCP's regulations require that food 2 5 operators set-up a mufti-step system designed to ensure food safety.
Rapidly cooling food immediately after the cooking process is one of these essential steps in assuring proper food quality.
The need for such rapid cooling systems results from the fact that all food 3 0 contains micro-organisms that are potentially dangerous. Most of them are destroyed by the cooking process. But those that survive (2% to 5%) can quickly regain their strength and begin to proliferate if given favorable conditions, such as in the critical temperatLUe zone situated between 15°C and 45°C.
Some can even reproduce at the frantic speed of once every 12 minutes : this means that one surviving bacterium will become one thousand bacteria after two hours, and one billion after seven hOllrS 1 It is often recommended that two hours be the maximum allowable cooling time.
This way, food stays within the critical zone for only a short period of time.
Under such conditions, risks of food poisoning are greatly reduced. The challenge is precisely to cool down large quantities of food in less than two hours.
The market has responded to the challenge with several types of rapid-cooling processes, one of them being called "quick chilling", sometimes called "blast chilling", in which food is cooled by a high-velocity flow of very cold air.
The air temperature within the cooling zone can go as low as -15°C. Standard-sized pans (20" X 12") having depths of 1 ", 2.5" or 4" are used to contain the food. The process, better adapted to smaller operations, is widely used.
Existing blast chillers have in common two major flaws. First, they simply cannot be properly cleaned. Cooling fans, fan motors, evaporator fins, etc., are practically impossible to clean and sanitize. After a short operating period, micro-2 0 organisms start proliferating on the various surfaces and are circulated onto the food itself by the air flow. The second major design defect is that evaporators will catch most of the humidity given off by the food, condense it in the form of droplets, and freeze it as soon as the evaporator's surface temperature falls below 0°C. Once the water freezes up, the air flow is partially blocked, which lengthens 2 5 the food-cooling process. The end result is that quick chillers often have to be defrosted after each cooling cycle. Most user's manuals recommend at least one defrost cycle per day. In some apparatus, the defrosting is done simply by leaving the door of the cooled space open while fans are running. This takes precious time. In most cases, an electrical resistance element is used for defrosting.
This 3 0 takes time and uses a lot of electrical energy.
Standard blast chillers also are quite noisy.~Not surprising, considering the fact that an 80 leg unit usually has several large axial fans to move the air around.

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fl~~ ai'~,r~~~~'f~cf CA 02476592 2004-08-17 "~~~~~~~t,~s~f 4 c~ .",~ ~r "v,~.~.,:;~Z ,, a.,.l Since fan motors are located within the cooled space, the heat energy given off by the motors, due to internal ine~ciencies, heats up the air which then has to be cooled down by the evaporator.
The cooling of food and the dehumidification of air are very closely related.
Indeed, in order to lower the food temperature, the air within the closed space where the food is placed must be dehumidified because of the heat and mass transfer process occurring between the food and the closed-space air. During this process, the air becomes more and more humid and reaches a saturation level.
Once this saturation level is reached, the air will not absorb anymore heat from the food until it looses some of its water vapor content. With that in mind, one can assume correctly hat some of the previously mentioned drawbacks which characterize conventional food-cooling apparatus will also be found in other dehumidifying systems such as air-conditioners, dehumidifiers, freezers, cold rooms, etc.
Summary of the invention A first object of the present invention ~is to provide a method for cooling and 2 0 dehumidifying air capable of overcoming the above mentioned drawbacks.
The method for cooling and dehumidifying air within a space comprises the following steps:
- forcing the air to be dehumidified into a cooling zone; and 2 5 - continuously evacuating from the cooling zone, droplets of condensed water resulting from condensation.
The method is characterized in that the cooling zone includes an evaporator plate having a plurality of fins forming air channels. The method further comprises the step of circulating air within the cooling zone in such a manner that the air 30 circulates within the air channels. The air is cooled and dehumidified by the evaporator plate. The humidity within the air is condensed on the evaporator plate.

it ~ s l~Q~' }a3z~t00~~ . CA 02476592 2004-08-17 ~~~Q,3~~r~~~'~~ s~~ff w ~«.1,..;r a~w.~...S.v~ . _.a. t= ~ ..~_ w ..ia t~~ ~;~sc Another object of the invention is to provide an apparatus for carrying out the method. The apparatus for cooling and dehumidifying air within a space comprises:
- a housing;
- at least one cooling zone located within the housing, the at least one cooling zone having at least one inlet in communication with the space, the at least one cooling zone also having at least one outlet in communication with the space;
- at least one fan for circulating air between the space and the at least one cooling zone; and - means located within the at least one cooling zone for continuously evacuating droplets of condensed water resulting from condensation.
The apparatus is characterized in that the at least one cooling zone includes at.
least .one evaporator plate located between the at least one inlet and outlet of the at least one cooling zone. The at least one evaporator plate has a plurality of fins forming air channels within which the air circulates.
.Another object of the invention is to provide an apparatus for cooling food.
The cooling apparatus for food comprises:
- an insulated housing;
- at least one food zone located -in the insulated housing for receiving food to be cooled, the at least one food zone having at least one inlet and at least one outlet;
- at least one cooling zone located within the insulated housing, the at least one cooling zone having at least one inlet in communication with the at Ieast one 2 5 outlet of the at least one food zone, the at least one cooling zone also having at least one outlet in communication with the at Ieast one inlet of the at least one food zone;
- at least one fan for circulating air between the at least one food zone and the at least one cooling zone; and 3 0 - means located within the at least one cooling zone for continuously evacuating droplets of condensed water resulting from condensation.
The cooling apparatus for food is characterized in that the at least one cooling zone includes at lest one evaporator plate located between the at least one inlet ,:.:: ,:. ...:....~".....,.."""..... ,., ~ .. .. ....
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s and outlet of the at least one cooling zone. The at least one evaporator plate has a plurality of fins forming air channels within which the air circulates.
One of the main advantages of the above apparatus for carrying out the same is that the evaporator plate can be completely cleaned and sanitized in a few minutes. Such substantially reduces the risk of contamination~normall-y present in conventional quick chillers. The result is a longer period of safe food storage.
Moreover, since the previous apparatus allows rapid shedding of any condensation off of the evaporator plate, freeze-ups never occur. The icing and defrosting processes are thus eliminated, which saves precious time and electrical energy.
In addition, the absence of ice improves the heat transfer process between the air and the refrigerant, so that a smaller compressor can be used.
The objects, advantages and other features of the present invention will become more apparent upon .reading of the following non-restrictive description of a preferred embodiment thereof, given for the purpose of exemplification only with 2 0 reference to the accompanying drav~iings.
Brief description of the drawings FIG. 1 is a front view of a cooling apparatus for food according to the preferred 2 5 embodiment of the invention, showing the insulated housing.
FIG. 2 is a side view of fine apparatus shown in figure 1.
FIG. 3 is a exploded perspective view of the apparatus shown in figure 1.
FIG. 4 is a perspective view of the apparatus shown in figure 1, which shows features within the apparatus.
30 FIG. 5 is a front view of the cooling zones diametrically opposed to each others.
FIG. 6 is a perspective view of the cooling zones diametrically opposed to each others.
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5a FIG. 7 is a top view of one of the cooling zones, showing the fins and the air channels.
FIG. 8 is a front view of one the cooling zones shown in figure 7.
FIG. 9 is a side view of one of the cooling zones shown in figures 7 and 8.
FIG. 10 is a front, cross-sectional view of one .side of the above apparatus showing the air flow within the cooling zone and the food zone.
FIG. 11 'is a front, cross-sectional view of the same apparatus showing the opposite cooling zones and food zone.
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FIG. 12 is a top plan view of the insulated ceiling.
FIG. 13 is a front elevational view of the insulated ceiling.
FIG. 14 is a cross-sectional view talcen along lines B-B of the insulated ceiling shown in figure 12.
FIG. 15 is a cross-sectional view taken along lines A-A of the insulated ceiling shown in figure 13.
FIG. 16 is a top perspective view of the insulated ceiling shown in figures 12 to 15.
FIG. 17 is a top plan view of the plate incorporating the fan inlet.
FIG. 18 is a perspective view of the vertical plate separating the cooling zone from the food zone.
FIG. 19 is a perspective view of a variant of the vertical plate shown in figure 18, which contains a plurality of openings.
FIG. 20 is a side elevational view of the plate incorporating the fan inlet shown in figure 17.
Detailed' description of a preferred embodiment of the invention Figures 1 and 2 are front and side elevational views of an apparatus 1 according 2 0 to a ~ preferred embodiment of the invention, which comprises an insulated housing 3, in which food may be stored. Figure 3 is an exploded view of the apparatus 1. Most of the components of said apparatus are preferably made of stainless steel, but plastic and aluminum could also be used.
As illustrated in figures 4, 5 and 6, the apparatus according to the preferred embodiment of the invention has two cooling zones 102, 104 each comprising one evaporator 101. Except where mentioned otherwise, both sides of the unit are symmetrical. Evaporator size may be approximately 74 cm wide, 56 cm high and 8 cm thick. Its fins 103 may be 5 cm deep and are distant from one another by 3 0 about 2,2 cm.
Figures 7 to 9 are showing evaporators 101 design featuring a large plate having long, deep, thick and smooth fins 103, with enough distance between them to create air channels 111 and permit the circulation of large volume of air flow.
Such a large distance between fms 103 also provides easy cleaning. The air flow travels along the evaporator 101, in between and along the fms 103. In standard evaporators, the air normally flows perpendicular to a bank of finned tube.
While circulating within the air channels 111, the air looses its humidity and heat contents.
Plates having fins are common in computers and the like, but in such cases, it is used for heat dissipation, not for heat absorption. The dissipation occurs through natural convection or via a forced, perpendicular air flow generated by an axial fan close to the plate. Moreover, in such cases, the fins do not serve as air chamzels.
In standard evaporators, the air normally flows perpendicularly to a finned tube, the fins themselves being very thin, fragile and very close to one another.
Humidity contained in the air condenses on the tube itself. The water droplets resulting from condensation freeze between the fins. This freezing process takes up precious cooling energy, which reduces system efficiency. The accumulated ice also reduces the available fin-to-air heat transfer surface, which further reduces system efficiency. The water freezing process continues until the passageway between fins is completely bloclced. The refrigeration system then has to be shut down and a defrosting process has to be initiated, which takes up precious time and requires electrical energy.
2 5 In figure 10, together with a vertical plate 115, said fins 103 form a large number of air channels 111 for the air to circulate and be cooled. Each of said fins 103 has a base and a tip and said fins 103 are thicker at the base than at the tip, providing good heat-transfer efficiency. Because of their size, shape and smooth surface, fins 103 are easy to hand clean and sanitize, either with a rag, a special brush or 3 0 even with a hot water hose. This prevents bacterial growth. Preferably, the distance between the fms is large enough to prevent droplets from touching at the same time to both sides of the channel formed by the fins, which would tend to improve adherence to surfaces and subsequent freezing of the condensed water droplets. A distance between fins of, say 6 mm or more, is recommended. Larger distances, say 15 mm and up, may also be provided for easier cleaning.
The evaporator can also provide some energy storage. Indeed, after an initial pre cooling of the system, there is a « hold » period during which the evaporator is kept at about 0°C. During this period, the mass of the evaporator helps reducing the number of On-Off cycles of the refrigeration system, improving its durability.
Figure 10 shows the path of air flow in and out of a food zone 201, on the left-hand side of the unit. When cooled air leaves evaporator 101 and arrives at the bottom of channel 123, droplets of condensed water are separated from the air flow by malting said air flow turn 90° and pass through an outlet 121 of the cooling zone 102 punched in the lower part of said plate 115. The heavy droplets, being unable to follow the same path because of the gravitational force, end up in a transversal cavity 125 and into a drain hole 141. Then, water is eventually drained outside of the apparatus 1 through an opening 143. A recipient for collecting water could also be used instead of a drain.
After passing through the outlet 121 of the cooling zone 102, the cold dry air is 2 0 forced to turn upwards through another 90° because of the presence of vertical plate 207. Said plates 115, 207 form a plenum 209 inside which said air can go up and be distributed into the food zone 201 via a plurality of openings 205.
Inside said food zone 201, the resulting horizontal jets 203 of cold dry air are mixed (because of the well-known entrainment effect) with the warmer, humid air above 2 5 the pans 501. The colder air flow circulating around the pans of hot food thus picks up heat energy and humidity. The result is a gradual cooling of the food through convection.
Each side of the unit has its own evaporator 101 and plenum chamber 209, and 3 0 both sides have symmetrical air flow paths, except that the left-hand side openings 20~ are offset with respect to the openings 205 of the same plate at the other side. Said offsets are chosen in such a way that the jets 203 directions alternate: for example, below the bottom pan 501, there is a left-hand-side jet 203 direction, while above said bottom pan 501, there is a horizontal, right-hand-side jet 203 direction.
The heated air is eventually pulled out from the food zone 201 by an outlet 211 of the food zone 201 by fan 401, pushed inside plenum 129 and then through a horizontal passageway 127 located above the food zone 201. Then, said air turns 90° and goes through a short, vertical passageway formed by plates 115 and 117, before arriving at the evaporator 101 and down between vertical fms 103 and plate 115, where a new cooling cycle begins.
The fan 401 is preferably of the radial or mixed flow type. Both types of fans can be efficient and very silent. Both also produce a greater pressure rise than the usual axial fans, which results in a higher speed flow of air along the fins 103.
This also helps in providing a uniform air distribution inside the apparatus 1. One large radial fan rotating at a relatively low speed (may be 1125 RPM) is normally preferable ; noise will be reduced and energy saved.
In figure 7 to 10, the finned evaporators 101 are preferably made of cast aluminum. They are cooled by an internal refrigerant circuit, consisting of a coil 2 0 113 embedded in the evaporators 1 O l during the casting operation. Said evaporators 101 are part of a common vapor-compression refrigeration system.
Now referring to figure 11, while fan 401 is located inside a cold, insulated zone, its motor 405 is located outside of said cooling zones 102, 104 above the 2 5 insulated ceiling 301, its driving shaft 403 going through a hole in the ceiling 301.
The ceiling is fabricated out of two'vacuum/heat formed plastic plates, separated by about 6 cm of urethane foam. Ceiling 301 and plate 303 provide the walls for plenum 129. Also shovv~m in figure 17 to 20, said plate 303 incorporates the fan inlet ring 305 and is hinged 133 to the internal baclc wall of the apparatus 1.
The boundaries of said cooling zones 102, 104, appearing in figure 11, are the insulated ceiling 301, the insulated vertical walls 119 and the insulated floor 145.
Figures 12 to 16 show the insulated ceiling 301.

Figures 17 to 20 show plates 115, 207, which form the left-hand-side and the right-hand-side plenums 209, are hinged 131 to the internal back wall of the apparatus 1. This way, they can be opened and closed like ordinary doors, for 5 cleaning purposes, or removed for repairs.
As mentioned earlier, in this apparatus 1, freeze ups cannot occur since condensed humidity cannot accumulate on the evaporators 101. Indeed, getting rid of the condensed water droplets can be facilitated in a number of ways:
the 10 evaporators 101 are installed vertically; air channels 111 between fins 103 are also vertical; air flows between fins 103, vertically from top to bottom; the air velocity is high between fins 103 (may be 10 m/s ~5); the fins 103 are smooth;
the fins 103 feature a hydrophobic coating such as Teflon.
Because of these characteristics, gravity helps water droplets to travel vertically down along the fms 103 and the air flow also helps water droplets to travel vertically down along the fins 103. The smoothing and hydrophobic coating of the fms 103 make the droplets slide down more easily along the fms 103.
Three plenums are built into the apparatus described above. The first plenum is located above food zone 201. Its function is to ensure a uniform horizontal air distribution through the evaporator fins 103, and thus a uniform cooling of the air.
The other two plenums 209 are located between vertical plates 115 and 117, on each side of the food zone 201. Their function is to ensure a uniform horizontal 2 5 and vertical distribution of cooled air in the food zone 201. This, in turn, produces a miform cooling of the food everywhere inside the food zone 201.
Plenums always have to be as large as possible. But again, a compromise has to be reached between plenum efficiency and global unit size.
Even though plenums are a common tool in heating and cooling systems, they are used here in a novel way, since they are installed in cascade, i.e. air goes through two plenums on its trip between the fan 401 and the food zone 201. Moreover, this is the only unit where the air flow is split in two before going to the evaporators. Finally, all three plenums can easily be opened and/or dismantled for cleaning purposes, which is a first.
It has been found experimentally that most of the water-vapor condensation occurs during the first part of the food-cooling cycle, while the food surface temperature is approximately above 10°C. Consequently, if the evaporator 101 temperature is kept at, say, 1 °C during that period, no icing will occur on the evaporator 101 surface; the water droplets will simply slide along said fins and accumulate at the bottom of the cooling zone where they will be collected by a transversal cavity 125, and will be drained 143 to the outside of the unit.
Control strategy also contributes to the elimination of defrosting cycles, which is an important time and energy-saving feature. Control of the evaporator 101 temperature can be obtained in a number of ways. The most usual technique being the use of the hot-gas-bypass technique, in which part of the flow of hot gases from a compressor outlet are sent directly to the evaporator 101 without first going through a condenser. By regulating, via a hot-gas-bypass valve (or HGBV), the quantity of gases going through the bypass, one can control the 2 0 evaporator 1 O l temperatur e.
It has also been found, however, that even when the evaporator temperature is not kept under control during the cooling process, very good results are still obtained, hardly any freezing will occur on the plate. Most of the humidity has already 2 5 condensed when the plate temperature gets below 0°C. This provides for much simpler controls.
As soon as the food surface temperature has dropped approximately below 10°C
(and/or the air temperature within the food zone has dropped to 4°C
3 0 approximately), the evaporator 1 O 1 surface temperature can be allowed to drop to a second set-point temperature of approximately -20°C, with no fear of evaporator-surface icing, since very little humidity is then circulated.

As the food core temperature reaches the desired final set point temperature, two methods can be used for ending the rapid-cooling process to avoid the freezing of the food. One method is to stop the compressor and let the evaporator 101 temperature come back to the first set-point temperature of 1 °C, the fan 401 still circulating the air. The other method is to keep the compressor running, but use the HGBV to send hot refrigerant gas into the evaporator 101 until it warm up to approximately 3°C. Then, after closing the HGBV, the system would let the system run and come back to the first set-point temperature of 1 °C.
From then on, the control system acts as a thermostat trying to lceep the air temperature at about 3°C, just like in a standard refrigerator. The core temperature will then slowly come down from 10°C to 3°C. Of course, all these set points are adjustable.
Alternative embodiments Although the present invention has been explained hereinabove by way of a preferred embodiment thereof, it should be pointed out that any modifications to this preferred embodiment within the scope of the appended claims is not deemed 2 0 to alter or change the nature and scope of the present invention.
Several alternative embodiments of the present invention can be created. For example, a prototype unit according to the present invention has been build.
The unit has a nominal capacity of 40 lcg of solid food (e.g. meat, vegetables, pastry, 2 5 etc.) and accommodates up to 10 standard-size pans. The unit has two evaporators. A refrigeration compressor has 1.5 hp, or about 25 % less hp than a refrigeration compressor in a conventional chiller.
Another apparatus for cooling food according to the present invention having a 3 0 lcg food capacity has been designed, built and tested, featuring a single vertical evaporator located vertically on a right-hand side of a food zone. The evaporator, including its fins, was 40 cm long, 50 cm high and 9 cm thick. The air flow was generated by a single centrifugal or radial fan also located vertically on the right-hand side of the food zone. In this apparatus, air to be cooled is pushed by the fan through a thin, wide passageway, through the top of the evaporator, and then down along the evaporator, between its vertical fins. When cooled air leaves the evaporator, droplets of condensed water are separated from the air flow by malting said air flow turn 90°. The heavy droplets; being unable to follow the same path because of the gravitational force, end up in a transversal cavity and into a drain hole. The air flow then travel horizontally to the left through a passageway and then up through a plenum, from which the air is distributed into the food zone through openings for cooling the food. The colder air flow circulating around the pans of hot food thus picks up heat energy and humidity.
The result is a gradual cooling of the food through convection.
The preferred embodiment of the invention features a single radial fan.
However, provided some modifications are made to the design of the unit, other types of fans could be used. Furthermore, two or more fans could be used. There are advantages to using a single, large fan, rotating at low speed, instead of two or more smaller fans. Firstly, there is an significant cost reduction. Secondly, a single fan results in an important noise level reduction and in energy efficiency.
The apparatus for cooling food according to the present invention has a fan, which motor is located outside of the cooling zone, i.e. outside of the insulated housing. Several advantages are thus provided. Firstly, the cooling zone can be completely washed and sanitized using a water hose, without fear of electrical shocks. Secondly, heat loss from the motor of the fan is not transferred to the 2 5 cooling zone, thus reducing the heat to be removed from said cooling zone.
One or more evaporators can be used within the apparatus, but in practice, one or two evaporators are preferred. Those evaporators can be flat or curved. Even cylindrical ones are an interesting possibility.
Tests have also been successfully performed with a vertical evaporator having horizontal fins, the air then circulating horizontally between the fins. In such a case, the air velocity between fins had to be increased somewhat to between 5 and 15 m/s approximately, in order for the droplets to be dragged towards the drain.
Although long fins are preferred, shorter will do fine. Also, the fin pitch (distance between fins) can be varied at will, but there will always be a compromise to be reached between ease of cleaning and heat transfer efficiency.
Instead of being cast, the evaporator can be made from extruded aluminum profiles. In such a case, the front of the evaporator featured the deep longitudinal fms while its back featured a plurality of longitudinal grooves. The grooves featured have, say a 4.5 mm radius and a circular shaped bottom. The coil, fabricated using a plurality of straight copper tubes having, say a 7.~ mm-diameter, is designed to fit into the grooves. Proper thermal contact between the copper coil and the wall of the groove is first established by pouring hot liquid zinc into the groove. Results were excellent.
A simpler and cheaper method is also possible : the diameter of the straight copper tubes is chosen so that it closely fit into the circular grooves. After being positioned into the grooves, the tubes are partly flattened out using a press brake 2 0 to establish a very good mechanical and thermal contact between tubes and the aluminum extrusion.
Evaporators can be made from any suitable material, using any known fabrication process. They can be cooled by any suitable primary or secondary refrigerant.
For 2 5 example, such finned evaporators could be cooled using a circulating solution of glycol. Even pure water can be used in some of the applications mentioned below.
The cooling of the food is more efficient by controlling parameters such as the food-core temperature, the evaporator temperature and the air temperature within 3 0 the insulated housing. It should be mentioned, however, that even when controlled solely with a food-core probe and an on/off thermostat, the system will give very acceptable results. It will also work quite well with a simple timer.

The present invention has several other applications. It will be particularly useful in applications in which the circulated air must both be cooled and dehumidified, which is the case in air conditioners, air dehumidifiers, freezers, refrigerating rooms, etc.

Another application of the invention concerns air conditioners. In order for air conditioners to be efficient, they have to cool the air quickly and remove humidity efficiently. To ensure safety, they should also be very easy to clean.
Otherwise, users will neglect the cleaning task and micro-organisms will start 10 proliferating within the air circuit, especially in between the closely-spaced fms of the evaporator, which are most of the time filled with condensed water.
These problems are very similar to those facing the quick chiller designer. The present invention can provide a solution to these efficiency and safety problems by providing an apparatus that can be cleaned in a few minutes, while conventional 15 air conditioners simply cannot be cleaned properly.
Moreover, since condensed-water droplets are quickly eliminated from the evaporator surface, the heat transfer between the air and the evaporator is much improved. This permitted a slightly higher evaporating temperature of the refrigerant and thus a better operating coefficient of performance (COP) and a larger capacity of the system. Also, the quantity of water removed from the air in time unit is appreciably higher. The use of a centrifugal fan instead of the usual axial fan also gives an important reduction in noise level of the unit.
2 5 Another application of the invention concerns air dehumidifiers. In order for air dehumidifiers to be efficient, they should remove as much humidity as possible from the air. To ensure safety, they should also be very easy to clean. Theses are problems that can be solved by the present invention.
3 0 The present invention may also be used to condense water vapour generated, for example, by the action of the sun on salty or polluted water. The end product will then be potable water. After minor modifications and the addition of components for storing the condensed water, the invention will thus become an efficient desalination plant or a water purification system. People in regions around oceans or on tropical islands would welcome such a technology.
Such a desalination plant (or water purification system) could even be made very cheaply by eliminating the mechanical refrigeration system altogether, replacing it with a continuous salt water (or polluted water) circulation. This would work as long as the available water is about 10°C (or more) colder than the atmosphere.
Moreover, the plates having a plurality of fins forming air channels could be made out of formed thin sheet metal or even out of thin thermoformed plastic sheets. One possible design for the finned plates would be assembling two of the formed sheets back ~to back, the cold water circulating between the two finned sheets, preferably from bottom to top, while the flow of air on the outside, between fins, would preferably be vertically downward. The flow of air would be generated by a fan of any available type.
In all the preferred and alternative embodiments, it could be interesting to monitor operational parameters such as the evaporator temperature, the air temperature once it leaves the evaporator, the cooled-space air temperature. However, tests have shown that not monitoring these parameters did not have an important effect 2 0 on the efficiency of the apparatus. Monitoring the various parameters is however recommended for security reasons or to improve the durability of the components of the apparatus.
Of course, in the case of the blast chiller, the food-core temperature becomes an 2 5 important parameter that can be monitored in order to indicate to the refrigeration system when to stop the rapid-cooling process. The evaporation and condensation pressures also are important parameters that one might like to monitor, in order to avoid operating conditions that would decrease the life of the costly compressor.
3 0 In the above mentioned simplified desalination plant, there would be no real need for monitoring any of the operating parameters, except maybe the salt water flow.

Claims

1. A method for cooling and dehumidifying air within a space, comprising the steps of:
forcing said air to be dehumidified into a cooling zone; and continuously evacuating from said cooling zone, droplets of condensed water resulting from condensation, said method being characterized in that:
said cooling zone includes an evaporator plate having a plurality of fins forming air channels, and said method further comprises the step of circulating air within said cooling zone in such a manner that said air circulates within said air channels, said air being cooled and dehumidified by said evaporator plate, the humidity within said air being condensed on said evaporator plate.

2. A method according to claim 1, further comprising the following step:
preventing formation of a cold water layer on the surface of said evaporator plate by rapidly removing said droplets of condensed water from said surface of said evaporator plate.

3. A method according to any one of claims 1 and 2, wherein said droplets of condensed water are rapidly removed from said evaporator plate by circulating said air along said air channels, and are evacuated from said cooling zone before freezing.

4. A method according to any one of claims 1 to 3, wherein said air channels are being substantially vertical in such a manner that said air circulates substantially vertically downward.

5. A method according to any one of claims 1 to 4, wherein said fins are covered by a hydrophobic coating.

6. An apparatus for cooling and dehumidifying air within a space, comprising:
a housing;
at least one cooling zone located within said housing, said at least one cooling zone having at least one inlet in communication with said space, said at least one cooling zone also having at least one outlet in communication with said space;
at least one fan for circulating air between said space and said at least one cooling zone; and means located within said at least one cooling zone for continuously evacuating droplets of condensed water resulting from condensation, said apparatus being characterized in that said at least one cooling zone includes at least one evaporator plate located between said at least one inlet and outlet of said at least one cooling zone, said at least one evaporator plate having a plurality of fins forming air channels within which said air circulates.

7. An apparatus according to claim 6, wherein said air channels are being substantially vertical in such a manner that said air circulates substantially vertically downward.

8. An apparatus according to any one of claims 6 and 7, wherein said fins are covered by a hydrophobic coating.

9. An apparatus according to any one of claims 6 to 8, wherein said fan is devised to circulate air with enough velocity to remove said droplets of condensed water from said at least one evaporator plate.

10. An apparatus according to any one of claims 6 to 9, wherein said at least one evaporator plate comprises an internal refrigerant circuit embedded therein.

11. An apparatus according to any one of claims 6 to 10, wherein each of said fins has a base and a tip and said fins are thicker at the base than at the tip.

12. An apparatus according to any one of claims 6 to 11, wherein said means for evacuating droplets of condensed water comprises a drain.

13. An apparatus according to any one of claims 6 to 11, wherein said means for evacuating droplets of condensed water comprises a recipient for collecting water.

14. A cooling apparatus for food comprising:
an insulated housing;
at least one food zone located in said insulated housing for receiving food to be cooled, said at least one food zone having at least one inlet and at least one outlet;
at least one cooling zone located within said insulated housing, said at least one cooling zone having at least one inlet in communication with said at least one outlet of said at least one food zone, said at least one cooling zone also having at least one outlet in communication with said at least one inlet of said at least one food zone;
at least one fan for circulating air between said at least one food zone and said at least one cooling zone; and means located within said at least one cooling zone for continuously evacuating droplets of condensed water resulting from condensation, said cooling apparatus for food being characterized in that said at least one cooling zone includes at least one evaporator plate located between said at least one inlet and outlet of said at least one cooling zone, said at least one evaporator plate having a plurality of fins forming air channels within which said air circulates.

15. A cooling apparatus according to claim 14, wherein said air channels are being substantially vertical in such a manner that said air circulates substantially vertically downward.

16. A cooling apparatus according to any one of claims 14 and 15;
wherein said fins are covered by a hydrophobic coating.

17. A cooling apparatus according to any one of claims 14 to 16, wherein said fan is devised to circulate air with enough velocity to remove said droplets of condensed water from said at least one evaporator plate.

18. A cooling apparatus according to any one of claims 14 to 17, wherein said at least one evaporator plate comprises an internal refrigerant circuit embedded therein.

19. A cooling apparatus according to any one of claims 14 to 18, wherein each of said fins has a base and a tip and said fins are thicker at the base than at the tip.

20. A cooling apparatus according to any one of claims 14 to 19, wherein said means for evacuating droplets of condensed water comprises a drain.

21. A cooling apparatus according to any one of claims 14 to 19, wherein said means for evacuating droplets of condensed water comprises a recipient for collecting water.

22. A cooling apparatus according to any one of claims 14 to 21, wherein the housing comprises two sides opposite to each other, each of said sides having one of said at least one food zone with said at least one outlet of said one food zone located on top of it, each of said sides also comprising one of said at least one cooling zone and at least one opening located at a bottom of said at least one cooling zone, said opening defining said inlet of said at least one food zone and said outlet of said at least one cooling zone.

23. A cooling apparatus according to claim 22, wherein each of said sides is provided with a plate defining a plenum located within said at least one food zone, said plenum being in communication with said at least one inlet of said food zone, each of said plates being provided with a plurality of openings, the openings of each of said plates at one end being offset with respect to the openings of the same plate at the other end.