Refrigeration – Disparate apparatus utilized as heat source or absorber – With vapor compression system
Reexamination Certificate
2001-05-22
2003-09-09
Tanner, Harry B. (Department: 3744)
Refrigeration
Disparate apparatus utilized as heat source or absorber
With vapor compression system
C062S260000, C062S186000
Reexamination Certificate
active
06615602
ABSTRACT:
FIELD OF THE INVENTION
The invention claimed and disclosed herein pertains to environmental climate control systems, and particularly to heat pumps for commercial or residential use.
BACKGROUND OF THE INVENTION
A common environmental conditioning system (i.e., a heating, ventilation and air-conditioning, or “HVAC” system) is the heat pump. The heat pump essentially uses a refrigeration cycle to move heat energy from a first environment to a second environment. The system is called a “heat pump” because the temperature of the first environment is lower than the temperature of the second environment, and so the natural direction of heat transfer would be from the second environment to the first environment The heat pump reverses this natural flow of heat by “pumping” the heat energy from a colder, first environment to a warmer, second environment. So long as there is at least some energy in the first environment, and an appropriate heat transfer fluid is selected, it is possible to transfer heat against the natural direction of heat transfer. The advantage of using a heat pump is that it can consume less energy to perform the heat transfer process than would be used to directly heat the first environment For example, if electricity is used to operate a heat pump to heat a first space, and the alternative is to heat the space with an efficient electrical heater, then the heat pump will typically consume less energy than would be used to directly heat the space using the electrical heater. A heat pump can be an attractive source of heating and cooling an indoor environmental space where the outdoor temperature does not reach extreme lows in the winter, and where the cost of electrical energy (used to operate a compressor and a fan in the heat pump) is not too high. When the cost of electricity becomes very high, then heating with natural gas may be a more economical alternative. However, where natural gas is not available (for example, in a rural or a remote setting), then a heat pump can be an attractive source of environmental heating and cooling even where the cost of electricity is relatively high.
Heat pumps are typically configured to operate in one of two modes: a summer mode and a winter mode. (These modes are alternately, and respectively, known as “cooling mode” and “heating mode”.) In the winter mode, the heat pump moves energy from a source of energy to an indoor environment, such as a residence or a commercial building. In the summer mode, the heat pump moves energy from the indoor environment to another location. Many heat pumps are configured to be able to switch from one mode to the other. Thus, the heat pump can act to heat an indoor environment in the winter, and cool the same indoor environment in the summer. Known sources of energy that can be accessed by the heat pump for winter mode include solar heat, ground or earth heat, ambient air, water (such as a river), and waste heat. Waste heat is more common in an industrial environment where heat from commercial processes (such as incineration) can be accessed. If the heat pump is to be used in the summer mode, then the objective becomes locating a destination to which heat from the indoor environment can be transferred. Obviously, for winter mode it is preferable to locate a source of energy having a large amount of available energy, such as solar energy. For summer mode, it is preferable to identify a location to which the indoor heat can be pumped which is relatively cool and will thus accept a large amount of heat. If the heat pump is configured to be capable of switching between modes, then it is preferable to locate a source which can provide heat for the winter mode, yet accept heat in the summer mode. The most common source is to use the outside ambient (or atmospheric) air. In this case, the heat pump is known as an air-to-air heat pump, since it moves heat between the air in the indoor environment and the air in the outdoor atmosphere.
A basic schematic of a heat pump
5
is depicted in
FIG. 1A
, and the basic thermal cycle of the heat pump is depicted in
FIGS. 1B and 1C
.
FIG. 1A
actually depicts a refrigeration configuration, but it can be considered as one or the other modes of a heat pump, depending on whether the heat exchanger which is located in the indoor environment is acting as the condenser (heating mode), or an evaporator (cooling mode). The “heat pump”
5
thus comprises a condenser
10
(between points (
4
) and (
1
)), an expansion valve
20
(between points (
1
) and (
2
)), an evaporator
30
(between points (
2
) and (
3
)), and a compressor
40
(between points (
3
) and (
4
)). A refrigerant in vapor form is passed through the condenser
20
. Heat is extracted from the vapor, causing a temperature drop and a loss in enthalpy “h” between points (
4
) and (
1
) (see FIGS.
1
B and
1
C). As the vapor is passed through the condenser
10
, it condenses to a liquid. The liquid refrigerant is then passed through the expansion valve
20
where it is flashed to a vapor, lowering the temperature of the refrigerant (see
FIG. 1B
between points
1
and
2
). The cooled, vaporized refrigerant is then passed through the evaporator
30
where heat in the form of enthalpy “h” is added to the refrigerant (see
FIG. 1C
between points
2
and
3
). Note that very little (or no) temperature rise in the refrigerant occurs as the refrigerant passes through the evaporator (see
FIG. 1B
between points
2
and
3
). The refrigerant vapor then passes through the compressor
40
, where heat in the form of sensible heat (indicated by a rise in temperature T, as indicated in
FIG. 1B
between points
3
and
4
), as well as enthalpy (
FIG. 1C
, between points
3
and
4
) is added to the refrigerant. The pressure of the refrigerant is also increased, providing a motive source to circulate the refrigerant through the system
5
.
Turning to
FIG. 1
, a prior art air-to-air heat pump is depicted in a schematic diagram. The heat pump
100
is depicted as operating in the winter “heating” mode. The heat pump uses a heat transfer fluid or refrigerant (not shown) which flows in the various fluid lines in order to transfer heat from an outdoor atmosphere “A” to an indoor environment “E”. A common refrigerant used in such heat pumps is a refrigerant known as “R-22”. The refrigerant is selected to have a flash point above the coldest anticipated outdoor temperature so that the refrigerant will still flash from a liquid to a vapor and thus absorb heat, as will be explained below.
The heat pump
100
comprises an indoor unit
102
and an outdoor unit
104
. The indoor unit is located in the environment to be heated (such as a residence or an office building), and the outdoor unit is typically located out of doors and has access to the outdoor atmosphere. The indoor unit
102
comprises an indoor heat exchanger
108
comprising a series of coils or passes of fluid line through which the refrigerant passes. The coils are exposed to air from the indoor environment which is forceably passed over the coils by a blower
110
. If a fluid in the coils
108
is at a temperature higher than the temperature of the environment “E”, then heat energy from the coils
108
will be transferred to the environment air. The indoor unit
102
can further comprise a secondary heat source such as electrical heating element
111
which can be used to augment the heat from the coils
108
. In the heating mode depicted in
FIG. 1
, the exchanger
108
acts as a condenser such that the refrigerant enters the top of the exchanger
108
through line
106
as a vapor. As the environmental air is passed over the coils and heat is extracted from the refrigerant, the refrigerant condenses to a liquid and passes out of the bottom of the exchanger via the distributor
112
. The liquid refrigerant then passes through the check valve
114
and into the line
120
. Although a small amount of refrigerant may also pass through the TEV
116
, the bulk of the liquid refrigerant will pass through the check valve
114
.) The indoor unit is also provided with
Reid John S.
Reidlaw, L.L.C.
Tanner Harry B.
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