Heat Pump



Background

As a result of society's increasing concern for ecological and environmental issues, the demand for more efficient ways to utilize heat and energy is rising. The heat pump industry uses technological advances such as year-round space heating to displace heat energy to a more useful location and purpose. This concept is accomplished by providing localized or redirected heat, while exchanging cool air with heated air.

The principles of heat pumps are actually the reverse of the technological and thermodynamic principles of an air conditioner unit. The majority of heat pumps give the added benefit of providing both heating in the winter and cooling in the summer. This can be accomplished simply by reversing the flow of the working fluid circulating through the coils. The heat pump is an entire thermodynamic system whereby a liquid and/or gas medium is pumped through an assembly where it changes phases as a result of altering pressure. Although relatively costly to setup, the heat pump system provides a more economical and efficient way to control temperatures and reuse existing heat energy.

Raw Materials

The manufacturing of heat pumps involves the use of large iron castings with stainless steel components and aluminum tubing. The castings, used in the pump and motor, will often have small amounts of nickel, molybdenum, and magnesium to improve the mechanical and corrosion-resisting characteristics of the casting. In smaller heat pumps, some components require the use of alloy steel to reduce weight. Depending on what type of working fluid is used (ammonia, water, or chlorofluorocarbons), the piping in the heat pump system may require corrosion resistant stainless steel or aluminum. In systems where consistency of thermodynamic properties are more critical, copper tubing may improve efficiency. Housing most of the components of the heat pump, the encasements are fabricated out of mild carbon sheet steel. The rest of the piping, fittings, valves, and couplings are stainless steel.

All heat pumps require a working fluid to transfer excess energy from one heat source to another. Traditionally, chlorofluorocarbons (CFCs) have been used as working fluids because of their superior thermodynamic properties. Because of the harmful effects CFCs are now known to have on the environment, they have been gradually phased out of production. Instead, water, hydrocarbons, and ammonia are frequently utilized in heat pump systems despite their lack of efficiency in some heat pump designs.

Design

Heat pumps all have the same basic components. These components consist of a pump, a condenser, an evaporator, and an expansion valve. Despite the relative similarities of these components, heat pump designs vary greatly depending on the specific application of the pump. The two major designs, vapor compression and absorption, utilize different thermodynamic principles, yet both include similar components and provide similar system efficiencies.

Heat pumps demonstrate remarkable versatility in providing both air conditioning and heating in the same system by simply reversing the direction of flow of the working fluid. In this regard, heat pumps eliminate the need for dual systems in order to maintain a desired temperature. However, this will be costly as it requires a system that is able to pump in both directions. In extremely adverse climates, heat pumps lose some of their effectiveness and may require an additional heat source. This supplemental heat can come from geothermally heated water or electric heaters.

The typical heat pump operation uses the working fluid to receive heat from a source positioned close to the evaporator. At the evaporator, the fluid vaporizes into a low pressure vapor. Upon entering the pump, the vapor is compressed to high pressure and enters a condenser which returns the vapor to a liquid and ultimately gives off its stored heat to the desired source. An expansion valve then allows the system to return to its low pressure liquid state, and the cycle begins again.

The Manufacturing
Process

The pump is usually procured as a finished unit and installed into the system by integrating it with coupling and piping components. Designed for the specific size and fluid requirements of the system, the pump may be shipped, depending upon its size, directly to the installation site. This usually occurs with large commercial heat pumps supplying heat and/or refrigeration to office buildings. Smaller residential models may have the pump installed into an assembly that includes the condenser, evaporator, and various piping. These units, encased in a sheet metal box, will be comprised of various subassemblies for the condenser and evaporator in order to bolt every component to the box or to one another. Some of the brackets used will form the base of the unit where the pump will be bolted down to a metal pan and connected to an AC motor.

Encasements

Condenser and evaporator

Tubing

Painting/coating

Packaging

Installation

Quality Control

Each component that is procured from an outside supplier will usually be inspected for dimensional compliance before being assembled. Other components will be checked during their fabrication to ensure quality. The final assembly will then be tested by filling it with the appropriate working fluid and connecting the system to a power source to turn the pump. By measuring, with transducers or switches, the temperature and pressure levels of the fluid in different stages, the final system can be checked against predetermined criteria.

The Future

With the rising energy costs, the demand for the efficient heat pump will increase. The high initial cost will be returned in full as overall energy use decreases. The versatile heat pump will benefit organizations that aim to increase their exposure to new technological developments. As technology improves, the heat pump will ultimately produce more cost effective heating and cooling. Product development will generate competition among industries, causing the high manufacturing costs to decrease. Working fluid technology will continue to expand due to several experimental studies designed to meet future environmental concerns.

Where to Learn More

Other

"HydroHeat Geothermal Systems." October 4,1996. http://www.njhpc.org/njh_uses.html (July 9, 1997).

"Heat Pump Working Fluids." October 1996. http://www.heatpumpcentre.org/hpcwrkf.htm (July 9, 1997).

"Heat Pump Technology." October 1995. http://www.heatpumpcentre.org/hpctek.htm (July 9, 1997).

"Heat Pumps in Industry." October 1996. http://www.heatpumpcentre.org/hpciapp.htm#industrysystems (July 9, 1997).

Jason Rude



Also read article about Heat Pump from Wikipedia

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