Abstract:
A heat exchanger within a sheet metal enclosure includes mounting structure that provides double vibration isolation to minimize noise. The mounting structure includes at least one resilient vibration isolator that couples the heat exchanger to a vibration isolation plate, and includes other similar isolators that couple the plate to the enclosure. The mass of the plate is sufficient to somewhat emulate a dual mass/spring system having two degrees of freedom. To this end, the plate is preferably thicker than the sheet metal walls of the enclosure. The double vibration isolated heat exchanger is especially applicable to systems having several heat pumps that are mounted overhead. In some embodiments, the heat pump&#39;s refrigerant compressor is also resiliently mounted to the vibration isolation plate.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The subject invention generally pertains to a heat exchanger and more specifically to a mounting structure that provides the heat exchanger with double vibration isolation. 
     2. Description of Related Art 
     A typical water-source heat pump includes a compressor that compresses and circulates refrigerant in series-flow through two heat exchangers and a flow restriction (e.g., an expansion valve). One heat exchanger transfers heat between the refrigerant and an external source of water (e.g., ground water). The other heat exchanger transfers heat between the refrigerant and a comfort zone, such as a room or other area within a building. Often a four-way valve determines whether the heat pump heats or cools the comfort zone by selectively directing the refrigerant flow in a forward or reverse direction. 
     Heat pumps are often, but not always, installed as a system of several heat pumps, where each individual heat pump serves its own particular zone within a building, such as an apartment unit, hotel room, dormitory room, or classroom. A network of pipes interconnecting the heat pumps typically conveys water to and from each individual unit. Each heat pump unit often has its own supply and return air duct for its particular comfort zone. 
     When heat pumps are installed as a system of several units, often the most convenient location to install the units, the water piping, and the air ducts is overhead, or above the ceiling of each comfort zone. With the heat pumps in such proximity with the comfort zones, it becomes important to minimize any noise generated by the heat pumps. Noise is primarily created by the components that have moving parts, such as the compressor and a blower that forces the conditioned air through the room. 
     To provide a cushioned mounting for blowers or to minimize noise created by a compressor, such components can be mounted using vibration isolators, such as rubber grommets. Examples of such isolators are shown in U.S. Pat. Nos. 2,711,285; 4,984,971; 5,839,295; and 5,306,121. Further isolation can be achieved by installing an intermediate mounting plate between the compressor and a stationary base, as shown in the &#39;971, &#39;295, and &#39;121 patents. 
     However, in conventional heat pumps, the effectiveness of a high performance compressor isolation system can be compromised by vibration and/or pressure pulsations transmitted to auxiliary components in direct contact with the compressor. One such component is the water-to-refrigerant heat exchanger. Typically, these components are not isolation mounted. Vibration transmission from the compressor to the unit structure via these components can become the controlling factor in heat pump noise. 
     SUMMARY OF THE INVENTION 
     To minimize noise that could be created by a heat exchanger vibrating its surrounding enclosure or ductwork, it is an object of the invention to provide the heat exchanger with double vibration isolation. 
     Another object of the invention is to provide a heat exchanger with double vibration isolation using an intermediate vibration isolation plate that is of sufficient mass to isolate the heat exchanger more effectively than would be possible with a single layer of isolation. 
     A further object is to provide a heat exchanger with double vibration isolation using an intermediate vibration isolation plate that is thicker than the sheet metal of an enclosure in which the heat exchanger is installed. 
     A still further object of the invention is to provide double vibration isolation for a compressor and heat exchanger combination. 
     Yet another object is to provide a heat pump having two heat exchangers coupled to a compressor, wherein the heat exchanger closest to the compressor is provided with double vibration isolation to reduce noise, while the other heat exchanger is more firmly mounted to add rigidity to an enclosure that surrounds the heat pump. 
     Another object of the invention is to install a network of heat pumps and its associated piping and ductwork above several comfort zones, while providing each heat pump with double vibration isolation that includes an intermediate vibration isolation plate interposed between the comfort zone and a heat exchanger of the heat pump. 
     These and other objects of the invention are provided by a heat exchanger that is coupled to a vibration isolation plate by way of a first resilient member, while a second resilient member couples the plate to an enclosure that contains the heat exchanger. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a heat pump incorporating the subject invention with some portions of the heat pump being schematically illustrated. 
     FIG. 2 is a cross-sectional view of a building with a heat exchange system that includes several interconnected heat pumps, each of which incorporate the subject invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 1, a heat exchanger  10  is installed with double vibration isolation within a sheet metal enclosure  12 . Although heat exchanger  10  is readily applied to a variety of heating, ventilating, and air conditioning systems, it is preferably incorporated within a heat pump  14 . Thus, a preferred embodiment of the invention will be described with reference to heat pump  14 . 
     In this example, heat pump  14  includes sheet metal enclosure  12 , a refrigerant compressor  16 , a solenoid actuated directional valve  18 , heat exchanger  10 , a flow restriction  20  (e.g., an expansion valve), a second heat exchanger  22 , and a blower  24 . Valve  18  determines the direction of refrigerant flow to render heat pump  14  selectively operable in a heating or cooling mode. 
     In the cooling mode, valve  18  is positioned as shown to direct relatively hot, pressurized refrigerant from a discharge port  26  of compressor  16  into a port  28  of heat exchanger  10 . The refrigerant passes through heat exchanger  10  before discharging through a second port  30  of heat exchanger  10 . Heat exchanger  10  places the refrigerant in heat transfer relationship with a second fluid, such as ground water, well water, municipal water, etc. A liquid supply line  32  and a liquid return line  34  respectively convey the water to and from ports  36  and  38  of heat exchanger  10 . In this example, refrigerant-to-liquid heat transfer within heat exchanger  10  is provided by conveying the water through an inner tube  40  of heat exchanger  10  and conveying the refrigerant between the exterior of inner tube  40  and an outer tube  42  of heat exchanger  10 . Tubes  40  and  42  are both helically coiled with inner tube  40  being disposed within outer tube  42 . In the cooling mode, the water cools the pressurized refrigerant in heat exchanger  10 . The still pressurized, but cooler refrigerant discharging from port  36  passes through flow restriction  20 . Upon passing through restriction  20 , the refrigerant&#39;s pressure and temperature decreases. The refrigerant downstream of restriction  20  then passes through heat exchanger  22  to place the relatively cool refrigerant in heat transfer relationship with a current of air  44  created by blower  24 . The current of air  44  generally moves from a return air chamber  46  to a supply air duct  48 . The refrigerant in refrigerant-to-air heat exchanger  22  cools air  44 , which in turn is conveyed onto a comfort zone  50  (FIG. 2) by way of air duct  48 . Refrigerant having been warmed by air  44  is returned to a suction port  52  of compressor  16  to repeat the refrigerant cycle. 
     In the heating mode, valve  18  shifts so that a port  54  within valve  18  directs pressurized refrigerant from compressor  16  into heat exchanger  22 , where the relatively hot refrigerant now warms, rather than cools air  44 . From heat exchanger  22 , the refrigerant passes through restriction  20  to provide relatively cool, lower pressure refrigerant to heat exchanger  10 . In heat exchanger  10 , the refrigerant absorbs heat from the water passing through inner tube  40 . Another port  56  of valve  18  then directs the warmer refrigerant back to suction port  52  to repeat the refrigerant cycle in the heating mode. 
     Heat pumps, such as heat pump  14 , lend themselves well to a heat exchange system  58  where several heat pumps  14  interconnected by liquid lines  32  and  34  independently serve several comfort zones  60  within a building  62 , as shown in FIG.  2 . In the illustrated example, each heat pump  14  is in fluid communication with a comfort zone  60  by way of supply air duct  48  downstream of blower  24  and a return air duct  64  feeding chamber  46 . In such a system, the most convenient location for installing the heat pumps is often overhead, above the comfort zone they serve. When installed at such a location, it becomes very important to minimize any noise caused by heat pumps  14 . 
     Typically, noise originates at the compressor, which tends to vibrate due to its moving parts. However, compressor  16  being rather rigidly piped a relatively short distance to heat exchanger  10  causes heat exchanger  10  to vibrate as well. If not dealt with, the vibration of heat exchanger  10  can transfer to a sheet metal wall  66  along a top, bottom, and/or side of enclosure  12 . Vibration of sheet metal often produces objectionable noise, due to the relatively large surface area of the sheet metal and its other physical characteristics. 
     To minimize the noise, a vibration isolation plate  68  is interposed between heat exchanger  10  and wall  66 , i.e., plate  68  couples heat exchanger  10  to wall  66 , but is not necessarily physically “between” heat exchanger  10  and any particular wall  66 . For example, plate  68  should be considered as being interposed between heat exchanger  10  and an upper sheet metal wall  66  of enclosure  12 . A first resilient member  70  or isolator, such a rubber or polymeric grommet or spring provides a vibration-absorbing connection between plate  68  and a bracket  72  of heat exchanger  10 . A bolt  74  fastens isolator  70  to plate  68 . A second resilient member  76  (one or more) similar to isolator  70  provides a vibration-absorbing connection between plate  68  and enclosure  12 . Another bolt  78  fastens isolator  76  to enclosure  12 . 
     Together, the mass of heat exchanger  10 , the mass of plate  68 , and isolators  70  and  76  emulate a dual mass/spring system having two degrees of freedom. Ideally, the resulting vibration or noise transmitted to enclosure  12  has two high-response frequencies, rather than one as found in a simple mass/spring system having one degree of freedom. As a result, the amplitude of vibration drops off significantly at frequencies above the two high-response frequencies to provide a quieter system overall. To achieve such results, it has been found that vibration isolation plate  68  should have an appreciable amount of mass. More specifically, the thickness of plate  68  is preferably thicker than the sheet metal thickness of enclosure wall  66  (along the top, bottom, and/or side of the enclosure). In one embodiment, plate  68  is made of 10-gage sheet metal, while a significant portion of enclosure wall  66  is made of 18-gage sheet metal. 
     Although isolator  70  is the primary “spring” between heat exchanger  10  and plate  68 , some additional spring-effect is provided by the resilience of bracket  72  itself. It would also be well within the scope of the invention for the resilience of bracket  72  alone to provide all the spring effect. In such a case, bracket  72  would then be considered as a first resilient member coupling heat exchanger  10  to plate  68 . 
     In some embodiments, as shown in FIG. 1, a third resilient member  80 , plus a bolt  82 , couples compressor  16  to plate  68 . This helps isolate vibration of compressor  16  relative to plate  68 . 
     It should be appreciated by those skilled in the art that the actual structure of isolators  70 ,  76  and  80  can vary and yet still remain within the scope of the invention. Isolator  84 , for example, basically combines isolator  76  and  80  as a single unitary piece. In other words, rather than discrete individual elements, isolators  76  and  80  basically become an integral extension of each other. An example of isolators  70 ,  76  and  80  includes, but is not limited to, a model J4624 manufactured by Lord Corporation of Erie, Pa. 
     In some embodiments, heat exchanger  10  is substantially fixed relative to enclosure  12 , which is readily done, since heat exchanger  22  is farther from compressor  16  than is heat exchanger  10 . The extra length of pipe or tubing results in less compressor vibration transferred to heat exchanger  22 . In some cases, heat exchanger  22  being fixed to enclosure  12  adds to the enclosure&#39;s overall rigidity, and thus reduces the enclosure&#39;s tendency to vibrate and emit noise. 
     Although the invention is described with respect to a preferred embodiment, various modifications thereto will be apparent to those skilled in the art. For example, in some embodiments, a solenoid-actuated valve is connected to supply line  32  or return line  34  to control the flow of water through heat exchanger  10 . The actual direction of airflow  14  in and out of enclosure  12  can be from any side, top or bottom of enclosure  12 . Other variations are also well within the scope of the invention. Therefore, the scope of the invention is to be determined by reference to the claims, which follow.