WO2000063036A1

WO2000063036A1 - Roof top air conditioner for motor vehicle

Info

Publication number: WO2000063036A1
Application number: PCT/US2000/007309
Authority: WO
Inventors: Jang-Jai Lee; Young-Kill Ahn; Jong-Ho Kim; Jeong-Un Lyu
Original assignee: Carrier Corporation
Priority date: 1999-04-15
Filing date: 2000-03-20
Publication date: 2000-10-26
Also published as: AU3900500A

Abstract

An air conditioner unit (10) that is adapted for mounting upon the roof (11) of a motor vehicle (12). The unit is seated upon a base pan (15) that provides a reservoir (48) for water beneath a heat exchanger (20) that functions as a condenser when the unit (10) is operated in a cooling mode. The heat exchanger fan is arranged to create a vortex in a region behind the heat exchanger for distributing (30) water in the reservoir over the heat exchanger (20). A raised drain (50) is placed in the floor of the reservoir (48) in the vortex region. The height of the drain (50) entrance is below the fan (30) so that water collected in the reservoir when frozen cannot adversely effect the fan or other component parts of the unit.

Description

ROOF TOP AIR CONDITIONER FOR MOTOR VEHICLE

This invention relates generally to a heat pump that is mounted upon the roof of a recreational vehicle (RN).

The term heat pump as herein used relates to an air conditioner unit that is capable of operating in a first mode to provide cooling to a conditioned region which, in this case, is the cabin of an RV (cooling mode) and a second mode to provide heating to the same region (heating mode). The term vortex is used herein to define a mass flow of fluid in which the flow is circulatory and in which the filament or thread of the vortex is the locus of the centers of the circulation and its strength is constant along the filament. Air conditioning units that are mounted upon the roofs of motor vehicles are exposed to rain and snow which can be combined with condensate from the unit and settled in the unit's base pan. Because most motor vehicles are exposed to outdoor weather conditions which can change rather dramatically in a relative sort period of time, moisture collected in the base pan of a roof top unit can freeze while the unit is idle. Most rooftop air conditioner units have a low profile and, as a consequence, the fans associated with the heat exchangers generally operate with little clearance above the unit base pan. In the event moisture that is collected in the base pan freezes, the ice can seize a portion of at least one of the fans so that when the idle unit is placed in operation, the fan and related components can be damaged. o Although devices are known which can be utilized to melt ice, these devices are generally costly to implement, space consuming, and can be a drain on a motor vehicle's electrical supply. The base pans of some window air conditioner units are provided with drains, however, the drains are typically located in low areas well away from the unit fans. 5 It is a primary object of the present invention to improve air conditioning units and, in particular, heat pump units that are mounted upon the rooftop of a recreational vehicle. This and other objects of the present invention are attained by means of a base pan that is secured to the rooftop of a motor vehicle upon which a heat pump is mounted. A heat exchanger is positioned along one end of the unit base pan and a fan is located behind the back surface of the heat exchanger. A vortex region is created over the pan adjacent the heat exchanger when the fan is in operation. A reservoir is located in the pan beneath the fan for collecting water. The water is drawn up by the vortex effect and distributed over the surface of the heat exchanger. A drain hole is formed in the pan within the vortex region which allows water to drain from the reservoir when the fan is inoperative to a level to prevent ice from forming about the fan during periods when the unit is exposed to low temperatures.

For a better understanding of these and other objects of the present invention, reference will be made to the following detailed description of the invention which is to be read in association with the accompanying drawing, wherein:

FIG. 1 is a partial perspective view illustrating a heat pump unit that is mounted upon the roof of a motor vehicle such as a recreational vehicle;

FIG. 2 is an enlarged side elevation in section showing the heat pump unit illustrated in Fig. 1 in greater detail;.

Fig. 3 is a partial top view of the heat pump of the present invention showing the vortex effect produced by a heat exchanger fan; Fig. 4 is an enlarged side elevation of the heat pump shown in Fig. 3 further illustrating a reservoir for collecting water in the base pan of the unit and the vortex effect created by the heat exchanger fan;

Fig. 5 is a partial top view similar to that illustrated in Fig. 3 showing how water collects in the reservoir when the heat exchanger fan is inoperative; and Fig. 6 is a side elevation of the heat pump shown in Fig. 5 further illustrating how water collects in the reservoir when the heat exchanger fan is inoperative.

Turning initially to Fig. 1, there is illustrated a rooftop air conditioning unit generally referenced 10, that embodies the teachings of the present invention. The unit is mounted upon the cabin roof 11 of a motor vehicle 12, such as a motorized home or a recreational vehicle (RV). The unit includes a base pan 15 that is secured reduces the wind loading on the housing as the vehicle moves in a forward direction. The housing contains a series of elongated openings 19 that allow air to pass freely into and out of the unit. The housing and the base pan are molded of impact resistant plastic which is light-weight and exhibits high strength and ductility.

In many RV applications, the air conditioning unit is a heat pump capable of heating the cabin of the vehicle during cold periods and cooling the cabin during warmer periods. As noted above, water can collect and freeze in the pan of the unit when the vehicle is parked and not in use. The driver, upon starting the vehicle during a cold period, will change the mode of operation of the unit to the heating mode of operation. If, however, ice has built up around the heat exchanger fans, the unit can be severely damaged. Although the present invention is ideally suited to prevent ice from damaging a heat pump during cold weather operations, it is also designed equally well suited to enhance the performance of a conventional air conditioning unit and its applicability is not confined solely to use in association with a heat pump.

With further reference to Fig. 2, there is illustrated a rooftop air conditioning unit 10 mounted upon a base pan 15. The unit includes a first heat exchanger 20 that is mounted at the front end of the base pan and a second heat exchanger 22 mounted toward the rear of the unit. Heat exchanger 20 normally functions as a condenser when the unit is operating in a cooling mode, while heat exchanger 22 acts as an evaporator. The roles of the heat exchangers, of course, are reversed when the unit cycles into a heating mode. A motor 25 is located between the two heat exchangers. A blower 27 is connected to the motor via a first drive shaft 28. A fan 30 is also connected to the motor via a second drive shaft 31. The fan 30 is designed to pass air over and through heat exchanger 20 and discharge the air to the surrounding ambient through openings provided in the unit cover. The blower 27 is arranged to circulate conditioned air through the heat exchanger 22 and the cabin of the vehicle. The system compressor 33 is mounted upon the pan adjacent to the motor 25. Although 0 not shown, the components of the air conditioning unit are connected in a well known manner so that the unit can selectively be controlled to operate either in a cooling or a heating mode. Heat exchanger 22 and the blower 27 are enclosed with a split shroud having an upper section 36 and a lower section 37.

The heat exchanger fan 30 contains a slinger ring 39 that coacts with the fan blades to pick up water collected in a reservoir beneath the fan and distribute the water over the surface of the heat exchanger 20. When the heat exchanger is operating as a condenser in the cooling mode, the distribution of water over the heat exchanger surfaces enhances the performance of the condenser and thus the overall performance of the air conditioning unit. In operation, the fan creates a vortex of circular moving fluid that can include both air and water at the rear of the heat exchanger 20. The fan is located at a given distance from the heat exchanger surface such that the vortex region 45 (Figs. 3 and 4) encompasses a part of the base pan adjacent to the back of the heat exchanger.

With further reference to Figs. 3-6, a reservoir 48 is formed in the base pan immediately below the heat exchanger fan 30 in which water may collect due to rain, snow or condensation. The reservoir supplies water to the fan for distribution over the heat exchanger surface. A drain 50 is provided in the floor of the reservoir within the vortex region through which water in the reservoir can drain under the influence of gravity.

As illustrated, the drain, in this embodiment of the invention, includes a drain o pipe 51 that passes upwardly through the floor of the reservoir and is sealed in place to prevent leakage. The top entrance of the drain pipe is brought to a predetermined height above the floor of the reservoir so that water can collect in the reservoir when the units is not in operation. The level of the water collected in the reservoir is below the bottom surface of the fan 30. In the event water stored in the reservoir freezes 5 during periods of non-operation, the ice will not encompass the fan or otherwise impede operation of the unit. Accordingly, the unit can be safely placed in operation and the heating mode of operation selected without endangering the component parts of the unit.

The height that the drain entrance is brought to an elevation above the base 0 pan floor to about one-half the height that the lower section of the fan is elevated above the pan floor. It has been found that the system will circulate sufficient amounts of cooling water over the heat exchanger surface when the water level in the reservoir is maintained at about 0.100 inches.

As illustrated in Figs. 3 and 4, once the fan 30 is placed in operation, it will create a vortex behind the heat exchanger 20 in a region that encompasses the pan floor adjacent to the center of the heat exchanger. The entrance to the drain 50 is located within this vortex region. Because of the circular action of the fan induced vortex, the region around the drain entrance will remain relatively free of water when the fan is turning at its operational speed. At the same time, the fan pulls water from the reservoir and distribute the water over the back of the heat exchanger thereby enhancing the performance of the heat exchanger. The location of the drain entrance can be determined empirically with very little experimentation and is basically a function of the fan speed and geometry. As best illustrated in Fig. 4, when the fan is turning at operational speed, the vortex effect tends to force the water rearwardly, away from the drain, while at the same time distributing water over the back of the heat exchanger thus enhancing the performance of the heat exchanger when the unit is operating in a cooling mode.

Claims

We Claim: i 1. Apparatus for improving the performance of an air conditioning unit

2 that is characterized by, l a base pan upon which an air conditioner unit is mounted,

1 said air conditioner unit including a heat exchanger that functions as a

2 condenser, ι a fan mounted behind said heat exchanger with the axis of said fan being

2 perpendicular to the rear surface of said heat exchanger geometry,

3 a reservoir located in said base pan beneath said fan so that the bottom of the

4 fan is located a predetermined height above the reservoir floor,

5 said fan having a geometry such that it produces a vortex behind the heat

6 exchanger wherein water collected in the reservoir is distributed by the fan over the

7 heat exchanger, and

8 a drain means located in the reservoir within the vortex region.

i 2. The apparatus of claim 1 wherein said drain means has an entrance that

2 is raised to a predetermined height above the floor of the reservoir.

ι 3. The apparatus of claim 2 wherein wherein the height of the drain

2 entrance is below the fan's lowest section.

i 4. The apparatus of claim 3 wherein the height of the drain entrance about

2 the floor of the reservoir is about one half the height that the lowest section of the fan

3 is above the floor of said reservoir.

i 5. The apparatus of claim 4 wherein said base pan is mounted upon the

2 roof of a motor vehicle.

i 6. The apparatus of claim 5 wherein said air conditioner is a heat pump

2 and said heat exchanger operates as a condenser when said heat pump is in a cooling

3 mode.

7. The apparatus of claim 6 wherein said base pan is mounted on the roof of a motor vehicle and the heat pump provides conditioned air to the cabin of said vehicle.

8. The apparatus of Claim 1 wherein said fan is equipped with a slinger ring.

1 9. A method of improving the operation of a heat pump that is mounted

2 upon the roof of a motor vehicle that is characterized by the steps of, l mounting a base pan on the roof of a motor vehicle, l mounting a heat pump heat exchanger upon said base pan,

1 placing a fan upon said base pan so that the fan creates a vortex region over

2 the base pan adjacent to the back surface of said heat exchanger,

3 creating a reservoir in said pan beneath the fan for collecting water,

4 providing the fan with a geometry so that it will create a vortex behind the heat

5 exchanger over said reservoir, and

6 forming a drain within the vortex region, said drain having an entrance that is

7 raised above the floor of the reservoir to a height that is less than the height of the fan

8 above the floor of the reservoir.

1 10. The apparatus of claim 9 wherein the height of the drain opening is

2 elevated to a height that is about half the height of the fan above the floor of the

3 reservoir.