Combined ambient-air and earth exchange heat pump system

United States Patent [19]

Dressier

[54] COMBINED AMBIENT-AIR AND EARTH EXCHANGE HEAT PUMP SYSTEM

[76] Inventor: William E. Dressier, 20145 W. 119th St., Olathe, Kans.

[21] Appl. No.: 267,661
[22] Filed: Jun. 29, 1994

[51] Int. CI.6 F25B 27/02

[52] U.S. CI 62/160; 62/196.4; 62/200;

62/238.7; 62/260; 237/2 B

[58] Field of Search 62/160, 238.6,

62/238.1, 238.7, 196.4, 199, 198, 200, 324.1, 324.4, 260, 324.6; 165/45; 237/2 B

[56] References Cited

U.S. PATENT DOCUMENTS

3,782,132 1/1974 Lohoff 62/260

4,042,012 8/1977 Perry et al 165/1

4,065,938 1/1978 Jonsson 62/160

4,091,636 5/1978 Margen 62/260 X

4,143,642 3/1979 Beaulieu 62/238.6 X

4,165,036 8/1979 Meckler 237/2 B X

4,179,894 12/1979 Hughes 62/2

4,299,277 11/1981 McGregor 62/260

4,305,260 12/1981 Backlund 62/238.6

4,383,419 5/1983 Bottom 62/238.6

4,388,966 6/1983 Spiegel 165/45

4,409,796 10/1983 Fisher 62/160

4,423,602 1/1984 Venable 62/238.6

4,493,193 1/1985 Fisher 62/160

4,553,401 11/1985 Fisher 62/160

4,646,538 3/1987 Blackshaw et al 62/238.7

4,688,717 8/1987 Jungwirth 237/2 B

4,893,476 1/1990 Bos et al 62/79

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US005461876A

[li] Patent Number: 5,461,876 [45] Date of Patent: Oct. 31,1995

4,920,757 5/1990 Gazes et al 62/181

5,025,634 6/1991 Dressier 62/79

5,038,580 8/1991 Hart 62/260 X

5,224,357 7/1993 Galiyano et al 62/260

5,239,838 8/1993 Tressler 62/324.1

5,244,037 9/1993 Warnke 165/45 X

5,388,419 2/1995 Kaye 62/200 X

Primary Examiner—Harry B. Tanner

Attorney, Agent, or Firm—Simmons, Perrine, Albright &

Ellwood

[57] ABSTRACT

An improved combined ambient-air and earth exchange heat pump system includes a subterranean heat exchanger and an ambient-air heat exchanger, both refrigerant-based, which are adapted to be selectively operated individually, serially or in parallel for heating and cooling purposes. The system also includes a compressor, a dynamic load heat exchanger, a reversing valve for converting the system from heating to cooling and vice versa, storage for excess refrigerant including an accumulator, an optional preheat exchanger, a regulating assembly with bleed port arrangement, a bypass mechanism for repetitive start-up attempts, and a lost charge device. A control center is provided to automatically activate the ambient-air heat exchanger to assist the subterranean heat exchanger after thermal stressing about the latter, to automatically deactivate the ambient-air heat exchanger for ambient conditions below a preset temperature, to increase or decrease the number of tubes used by the subterranean heat exchanger, and to optionally maintain the flow of refrigerant through the subterranean heat exchanger in the same direction during both the heating mode and the cooling mode.

37 Claims, 2 Drawing Sheets

COMBINED AMBIENT-AIR AND EARTH EXCHANGE HEAT PUMP SYSTEM

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heating and cooling system for heating an environmental or process load by removing thermal energy from the earth and/or ambient atmosphere and transferring that energy to the load and, similarly, cooling the load by removing thermal energy therefrom and transferring that energy to the earth, and/or ambient atmosphere for dissipation therein.

2. Description of the Related Art

With the steadily increasing costs of fossil and other depletable types of fuels, which are presently being used to obtain desirable temperature levels in environmental and process loads, greater emphasis is being directed toward developing systems and methods to extract energy either from the vast, virtually unlimited thermal energy stored in the earth or from the ambient atmosphere and transferring that energy to the loads for heating purposes and, reversely, extracting thermal energy from the loads and transferring that energy either to the earth or to the ambient atmosphere for dissipation therein for cooling purposes. One type of previous system for accomplishing such objectives is commonly referred to as a heat pump.

Conventional air-source reverse-cycle heat pump systems are commonly used for providing heating and/or cooling to building environmental spaces, manufacturing processes, and a variety of other usages. Properly used, such systems can be quite effective in environments where the ambient temperature is not extreme. Although generally acceptable performance is obtained in such moderate ambient temperature conditions, such systems leave a lot to be desired during extreme fluctuations in ambient temperatures, wherein substantial reductions in heating and cooling capabilities and in operating efficiencies are realized.

Modifications in air-source heat-pump systems have been attempted to enhance performance, such as incorporating additional booster heat exchangers and/or secondary refrigerant loops. Unfortunately, such modifications have provided only minor enhancements at best.

In recent years, heat-pump systems have been developed which use subterranean heat exchangers whereby the earth is utilized as a heat source and/or sink, as appropriate. Heat-pump systems utilizing the more moderate temperature range of the earth provides efficiencies which are substantially improved over those obtained from air-source heat pump systems. Such earth exchange systems are based on the concept that useful thermal energy could be transferred to and from the earth by the use of subterranean tubes in flow communication with various above ground components.

A refrigerant coolant pumped through such tubes by a compressor serves as a carrier to convey thermal energy absorbed from the earth, as a heat source, to the above ground components for further distribution as desired for heating purposes. Similarly, the coolant carries thermal energy from the above ground components through the subterranean tubes for dissipation of heat energy into the earth, as a heat sink, for cooling purposes.

Unfortunately, a major complication may arise when refrigerant is pumped through the subterranean tubes. First, lubricant oil which characteristically escapes from the compressor while the system is operating is carried along with

the refrigerant throughout the system. Due to the lower elevation of the subterranean tubes, the lubricant oil tends to accumulate in the tubes. As a result, the accumulation of the lubricant oil in the subterranean tubes gradually floods those tubes, substantially reducing the ability of the subterranean tubes to perform their originally intended function. Further, the compressor may be gradually deprived of essential lubricant oil, which jeopardizes the continued successful operation of the compressor. As a result, various complicated refrigerant distribution configurations have been utilized in an attempt to control the flow of the refrigerant.

Second, when an energy demand cycle was completed, the system would shut down while waiting for a subsequent demand for energy transfer. As a result, a certain amount of liquid refrigerant then passing through the subterranean tubes would lose its momentum and remain in the subterranean tubes. When the subsequent energy demand occurred, the compressor, which was generally designed for pumping gas as opposed to pumping liquid, would quickly deplete the gaseous refrigerant trapped between the liquid refrigerant in the subterranean tubes and the compressor such that a low pressure condition was quickly created at the inlet of the compressor. Most compressors are designed to interpret such a low pressure condition at the inlet as an indication that insufficient refrigerant exists in the system to function properly. As a result, the compressor would automatically shut down when such a low pressure condition was sensed in order to protect against potential bum-out of the compressor from absence of sufficient refrigerant.

A similar but more pronounced low pressure problem was encountered when a reversible system switched from a heating mode to a cooling mode. This problem arose from an imbalance in the refrigerant capacity which is inherent in a reversing system. The imbalance results from the much larger volume capacity of the subterranean heat exchanger as compared to the volume capacity of the dynamic load heat exchanger. When the operating cycle reversed, additional time was required to transfer the excess refrigerant whereby the refrigerant could assume its appropriate redistribution throughout the system in order to properly function in the reverse mode.

During that transfer time period, the previously described low pressure condition was created at the inlet of the compressor. The generally, relatively short time interval allowed for the low pressure condition at the compressor inlet before automatic shutdown was generally insufficient for the compressor to overcome the inertial resistance of the static refrigerant in the subterranean tubes and to redistribute the refrigerant for the reverse mode. Again, the low pressure condition at the compressor inlet generally caused the compressor to automatically shut down prematurely. Such imbalance was particularly troublesome during a system start-up at the end of an extended heating cycle where the temperature of the earth surrounding the subterranean tubes has been reduced as a result of extraction of thermal energy therefrom. As a result, a large volume of refrigerant could accumulate in the tubes of the subterranean heat exchanger.

A third problem, which was generally observed for prior art heat pumps, was the absence of a mechanism for achieving refrigerant pressure equalization subsequent to system shutdown for reducing start-up loads. Because of the absence of such pressure equalization, the service life of the compressor was reduced.

Previous attempts to circumvent some of the aforesaid problems generally followed either of two approaches: (i) using a plurality of closed loop systems working in combi