Microenvironmental cooling system

A microenvironmental cooling system is disclosed. The microenvironmental system includes a pressure box or a pressure source upstream of an evaporator. Downstream of an evaporator is a personal cooling device, which is adapted to lay adjacent or on the skin of the user. The evaporator includes an evaporator coil (having fins and a coolant tube) and a housing and walls configured to direct the airflow through the housing, in several embodiments, multiple times across the longitudinal axis fins of the coil.

FIELD OF THE INVENTION

Heat exchanger based systems for use with personal cooling devices.

BACKGROUND OF THE INVENTION

Achieving human comfort by microenvironmental means is not a new concept. Man has been doing it for eons every time he wore a bearskin in his cave to protect himself against the cold or a coat against the chill of a winter's night in more modern times. These achieve warmth for the wearer because they prevent cool airflow from the outside reaching the skin of the user. Thus the trapped air is warmed by the body heat to near body temperature and the person feels comfortable. However, these garments must also ‘breathe’ and allow a small amount of escape of that warmed air in order to allow the skin's perspiration and its humidity to also escape. Otherwise that moisture is trapped against the skin and keeps the pores of the skin from allowing their moisture to escape effectively. This means our primary mechanism for regulating body temperature (sweating) is inhibited and the person will shortly become uncomfortable.

While microenvironmental heating is something man has done for millions of years, microenvironmental cooling is new. Do you really care what temperature exists in the back corner of the room on a hot summer's day? No, you only care about the 1-inch of air immediately surrounding you skin. You care not only about its temperature, but also about its humidity.

Heat Index is the ‘feels like’ temperature in hot conditions. It's primary components are ambient temperature and humidity. A 90° F. temperature with 40% humidity has a Heat Index “feels like” temperature of 91° F. Raise that humidity level to 90% and the Heat Index rises to 121.9° F. Raise both temperature and humidity to 100° F. and 100% humidity and the Heat Index is 195.3° F. Thus humidity, more that heat itself, is the primary driver of increased Heat Index and heat discomfort.

Whether the air is moving or still is not considered to be a component of Heat Index. Yet anyone working in hot humid conditions knows hot conditions in still air are far more miserable than the same conditions with a 2-3 mph breeze.

The human body's primary means for internal temperature regulation is sweating (transpiration) where body water is put out through the skin's pores as water or water vapor and so rids the body of its internal excess heat. As humidity rises, the gradient between the skin's pores and the outside environment is reduced finally to the point where water vapor can no longer flow from the skin to the outside (at 100% relative humidity). Now the body is inefficient at ridding itself of its heat, and heat begins to build up, causing more sweating as formation of liquid on the skin in an effort to rid the body of its excess heat.

If that person is in still air and the same relative position for long periods of time (as walking will cause the air and its heat/humidity in contact with the skin to move off the skin), his immediate environment becomes saturated with his own body moisture, either as liquid or humid vapor at his body temperature, Regardless of the actual temperature, the 1-inch of air immediately around him becomes nearly 100% humid and at (or even above) his core body temperature. If even a slight 2-3 mph breeze then begins to blow upon him, that humid vapor is blown away from him and he immediately begins to feel relief. His ability to transpire effectively is restored and he begins to feel cooler immediately with both his immediately surrounding temperature and humidity dropping as his personal Heat Index plummets. Comfort is restored.

Air-conditioning of indoor air began in the early 20th Century and is a comfort familiar to us all. Yet certain jobs and outdoor activities leave us uncomfortable as air-conditioning is not possible. Outdoor jobs, work in warehouses where air-conditioning is impractical, work in confining work clothes where one cannot feel air-conditioning such as a gowned surgeon at surgery, workers in HazMat or BioHazard total enclosure suits, firemen, furnace workers, flight-line workers, etc. all share hot sweaty work conditions as the working conditions prevent them from experiencing proper air-cooling. That is—until now.

SUMMARY OF THE INVENTION

Microenvironmental air-cooling (as opposed to air-conditioning which employs both heating and cooling to provide comfortable conditions for its users) brings the advantages of air-cooling to the personal space of workers previously denied such comfort by their job. The primary components of microenvironmental air-cooling (MAC) are a pressurized evaporator coil engineered (for a specified temperature range) to take the hot ambient air and produce an airstream of the desired final temperature in a single pass through the evaporator. Implicit in this MAC is a reduced but pressurized airflow through a properly sized evaporator through one of the alternate airflow paths attached and hereafter described. Pressurization is necessary to drive the airflow through these longer and more resistive alternate pathways, but the advantage is much higher heat extraction from the airflow and thus much colder air than can normally be produced by an air conditioner (14-17° F.ΔT in a regular air-conditioner, currently 80° F. ΔT in one of our working prototypes).

Also implicit in this assembly is an end-user device capable of confining the hyper-cold limited airflow to the 1-inch of space immediately upon the skin of the end-user (especially his trunk, head, and neck). This device must also make use of the pressurization to effect jets at critical points of the body (such as the armpits, neck, scalp, and back) and so create that 2-3 mph breeze inside the end-user device (such as a vest, a jacket (or other garment), a comforter, a total-enclosure suit, a shell over a cot, etc.). Thus the end-user can utilize the limited cold air to effectively cool his personal microenvironment.

As alternate pathway evaporators generate far colder than usual air-conditioning evaporators, there is a far greater propensity for condensation to form within these MAC evaporators. As these alternate pathway evaporators are sealed and pressurized, that condensate must be collected and drained from the evaporator so a water-trap obstruction cannot form (see, for example,FIG. 3). Because these alternate airflow evaporators are maintained near 0° C. (32° F.), that condensate can be copious. As draining such an amount may be otherwise messy, that condensate can be blown onto the condenser fins, thus increasing their cooling efficiency and adding to the overall efficiency of the system.

Implicit, but not obvious, is the last advantage of microenvironmental air-cooling via these alternate airflow pathways. Because humidity in the hot air condenses out within the evaporator as drainable water, the final air output is far drier than surrounding ambient air. Applicant has reduced 90% humidity ambient air to 36% humidity after a single pass through our prototype evaporator. As humidity is the most important component of Heat Index to comfort, this stripping of humidity from the microenvironmental airflow is THE factor that produces the greatest comfort for the end-user, much more than standard air-conditioning is capable of producing.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1illustrates the prior art showing an evaporator coil10having fins12and cooling tubes14engaged therewith. Hot air is seen making a single pass blowing from the right to the left across or parallel to the fin short axis.

FIGS. 2A and 2Billustrate an embodiment of Applicant's evaporator15. This embodiment uses evaporator coil16oriented with gravity so that the fin long axis is substantially vertical. Air flows along (not across) the long axis of the fins, in a single pass. Further, air, typically hot air coming in from the top, makes a single pass and exits a housing or encasement typically near the bottom thereof. At least some walls22, which may be walls of a housing or encasement, are placed adjacent the two opposed side edges of the vertically oriented coil so as to constrain the air moving from top to bottom as seen inFIG. 2B. Plenums26/28and a housing24as set forth in more detail below may be used with this embodiment.

InFIG. 3, another embodiment of Applicant's evaporator15is illustrated. In the embodiment ofFIG. 3, evaporator coil16is placed so that fins18are horizontal (vertical and horizontal with respect to gravity). Coolant tubes20are generally engaged through the fins as illustrated in the Figures. Here, walls22may be provided again to restrict the air to a single pass, illustrated inFIG. 3from left to right, horizontally along (not across) the long axis of the horizontal fins. Walls22may be some of the walls of an encasement or housing24.

The embodiment ofFIG. 3has an horizontal fin axis as compared to the embodiment ofFIGS. 2A and 2B, which has a vertical fin axis. Both embodiments constrain airflow to a single pass, along (not across) the fins. Moreover, the airflow is pressurized with a fan or a pressure source upstream of the inlet and therefore evaporator coil16is usually placed in an encasement or housing24with inlet36on an upstream side for receiving pressurized warm (ambient) air and an outlet36on a downstream side adjacent where cold air exits the evaporator15for providing cold pressurized air to a personal cooling device downstream thereof as set forth in more detail below.

Cooled warm air will typically generate some condensate and, inFIGS. 2A and 2B, the condensate may move downward, under the impetus of gravity, to collection tubes as set forth herein below. While the embodiment ofFIG. 3is generally provided vertically, it may be tilted a few degrees from the orientation illustrated inFIG. 3to help condensate flow off the edges thereof.

FIG. 3also illustrates the use of encasement or housing24, typically six walls surrounding the coil16, which walls are substantially airtight and may include upstream plenum26having inlet36for receipt of warm pressurized air and may also include downstream plenum28with outlet38, which plenum will collect the now cooled air and send it out outlet38for use in a personal air cooling device downstream thereof.

Housing or encasement24may also include at the bottom thereof, a catch basin30which walls may be angled and may have a collection tube32with a multiplicity of small holes at the base thereof. A drain34may engage the catch basin and/or the collection tube for draining condensate that will typically be generated as the warm air cools as it moves left to right through the airtight encasement. Encasement or housing24will typically have walls adjacent the short axis to the fins so air will be constrained to move from left to right as illustrated inFIG. 3, or top to bottom as illustrated inFIGS. 2A and 2B, which also can have a similar encasement, plenum, drain, etc.

FIGS. 2A, 2B, and 3all illustrate long axis flow of pressurized air. Likewise.FIG. 4illustrates the long axis of the airflow along the fins.FIG. 4illustrates, in addition to evaporator coil16with coolant tubes20and fins18, that a refrigerant thermostatic expansion valve40or capillary tube is typically used, as known in the art, to control the expansion of the coolant agent entering the evaporator coil16. Walls22are omitted, but are similar to the walls22ofFIGS. 2A and 2B, in that they will help constrain the airflow. However.FIG. 4uses typically a plurality of dividers42and/or airflow redirectors46, which will help constrain and direct the flow between endplates44so multiple passes are made up and down the long axis of vertically oriented fins. An upstream plenum26may be provided as illustrated inFIG. 4, as well as an inlet36for receiving warm ambient air and outlet38for expelling cool, drier air. Airflow redirectors46may engage the endplates and at least some of the dividers (alternate dividers as illustrated inFIG. 4), so as to allow multiple passes of the airflow with the long axis of the fins, noting however that the multiple passes are not multiple passes of the same air molecules on the same fins, but are passes through the sections48/50/52/54of the evaporator coil16as illustrated inFIG. 4. Dividers42typically represent common walls. Note that airflow redirectors46a/46bare located adjacent the bottom of the vertically oriented fins18. Under the impetus of gravity, condensate may form near the bottom of the airflow redirectors46a/46bor other lower walls and thus as in the previous embodiments, a collection tube32with many small holes may be used to drain off the condensate. Note that the embodiment ofFIG. 4, which may be described as a long axis serpentine alternate airflow pattern, will receive pressurized air as in the previous embodiments, but may use a typical prior art short fin evaporator with the fins kept vertical. This positioning allows water condensing on the fins to drop by gravity to the bottom airflow redirectors46, where the condensate is collected into condensate collection tube32or tubes beneath as illustrated. By this means, all condensate is collected and eliminated from the evaporator, thus ensuring that a water trap in the evaporator cannot occur.

Note that with the location of the thermostatic expansion valve40that the airflow pattern has its entry to the evaporator coil16through the warmest portion of the heat exchanger or evaporator coil and its exit adjacent the thermostatic expansion valve is typically where the evaporator coil is coldest and working at maximum efficiency. The dividers and redirectors simply force the pressurized airflow back through the evaporator coil16repeatedly in order to achieve maximum heat extraction and the coldest air possible. Walls, encasements or a housing in the embodiment illustrated inFIG. 4may be applied directly and sealed adjacent the short axis of the fins and engage the dividers and the airflow redirectors and endplates. As such, the short axis is blocked so that no airflow can flow through it and only long axis serpentine flow may be generated. Thus, walls are configured as illustrated inFIG. 4to generate serpentine long axis flow pressurized through a coil and available to a personal air cooling device downstream of outlet38.

FIGS. 5A and 5Brepresent yet another use of walls configured to generate a serpentine (multiple pass) alternate airflow through an evaporator coil16comprising an evaporator15for use with a personal air cooling device. InFIGS. 5A and 5B, however, there is a serpentine flow across the short axis of a vertically oriented coil. Here, fins18of evaporator coil16are placed in a vertical orientation. Encasement or housing22partially includes a multiplicity of airflow redirectors46(external walls). Encasement housing22may have external walls acting as airflow redirectors46. An upstream plenum26and a downstream plenum28is provided. As can be seen best inFIG. 5B, dividers42are staggered and are opposed so as to generate the serpentine airflow indicated by the arrows inFIG. 5Band the arrows inFIG. 5A. Note again cold air outlet38is adjacent thermostatic expansion valve40. Collection tube32may be used and floor43may be cantered slightly so the condensate, draining from top to bottom as seen inFIG. 5A, may run slightly downhill to the left, engage collection tube, and can be removed from the encasement or housing22.

Illustrated inFIGS. 5A and 5B, it can be seen that the encasement is engaged with dividers42, which are used in conjunction with the side walls and end walls as indicated to help redirect airflow so it passes multiple times across different short axis sections of the coil. With the use of the dividers, the encasement, and the inlet/outlet, the serpentine motion causes the airstream to be repetitively chilled with a final result being cold airflow. Typically, humidity will condense on the air fins and run vertically to the bottom of the encasement. The typically sloping floor43delivers condensate to the collection tube32. This water can be drained or, as the airflow is pressurized, can be blown onto the fans cooling the hot condenser heat exchanger. This will help cool the condenser more effectively while turning water condensate back into vapor which can be carried out in the airstream. Another effect is to increase the efficiency of the system as a whole.

FIGS. 6A and 6Billustrate a short axis cross-counter flow (FIG. 6A) and along axis cross-counter flow (FIG. 6B) embodiment of evaporator15. Cross-counter flow is another pressurized alternate pathway through evaporator15which results in greater heat extraction of the airstream passing through it as opposed to a normal, unpressurized single short axis pass through an evaporator. The inlet and the outlet are precisely in opposite positions on the housing surrounding the evaporator resulting in the most even distribution of airflow through the evaporator coil16. InFIGS. 6A and 6B, inlet of warm pressurized air36is provided to upstream air plenum36. Encasement or housing24is provided. InFIG. 6A, walls of the housing force air across the short axis, into downstream plenum28, out outlet38. InFIG. 6A, the fins are vertical, and inFIG. 6B, the fins are horizontal.

FIGS. 7A and 7Billustrate another embodiment of Applicant's evaporator. In this embodiment, the evaporator has multiple cylindrical disks56aligned parallel to one another and the disks having a multiplicity of openings58therein. The disks are physically contacted with a typically coiled coolant tube having an inlet at one end and an outlet at the other. An encasement is provided having a cylindrical side wall and typically planar end walls. The end walls will include an inlet and an upstream plenum and an outlet and a downstream plenum. The disks are typically maintained in a vertical position and there may be a collection tube at the lowest point of the cylindrical sidewall.

The spiraled or coiled effect is assisted in providing a slice at least partially through the disk and separating them slightly with a gap60in which the coiled coolant tubing can pass from one disk to the next. The spiraled or coiled airflow path is created by the intersecting of the split metal disks into a coil, or coaxial coils of different diameters, in the manner set forth inFIGS. 7A and 7B. While this device is a variation of lateral airflow path, the split disks will introduce some spiraling of the warm air entering the evaporator coil16from the upstream plenum. This device may be useful when constrained evaporator size dictate this designed smaller diameter. Air enters upstream plenum28through inlet36and percolates through the openings58with some rotation generated by gap60and cools as it passes through the cold mesh generated by the disks. Condensate may collect along the bottom cylindrical sidewall and pass through tube enclosure for draining.

Applicant's airflow in the embodiments illustrated, wherein the airflow is in contact with the fins, is typically at least 10 inches to achieve the relative humidity decrease necessary.

The following Figures of the '732 reference incorporated herein by reference show personal cooling devices62that lay on or adjacent the skin, and that are either worn by a user or lay on the user:FIGS. 21A, 21B, 21C, 22, 23A, 23B, 25A, 25B, 26, 27, 28, 29A, 29B, and 37. These include, typically, multiple tubes and multiple jets directed generally towards the skin of the wearer.

FIG. 8illustrates Applicant's system comprising a blower box64or other source of pressurized ambient air and an evaporator comprising one of the embodiments as set forth herein and a personal cooling device62being worn by a person. Note inFIG. 8, the evaporator is shown, but other elements of the coolant circuit, such as the condenser and the like, are known in the art and represent, typically, a remote condenser for releasing heat.

Although the invention has been described in connection with the preferred embodiment, it is not intended to limit the invention's particular form set forth, but on the contrary, it is intended to cover such alterations, modifications, and equivalences that may be included in the spirit and scope of the invention as defined by the appended claims.