The purpose of this page is to cover the fundamental principles explaining how heat pumps work, and provide practical details for anyone who is considering installing a heat pump. This practical detail consists of setup expense and running expense analysis, and provider listing. Heat pumps are a terrific creation and are quite fascinating from a physics point of view.
How Heat Pumps Work– The Basics
A heat pump is a gadget that “transportations” heat from one place to another location. This is the basic function of how heat pumps work. An air conditioning unit is a form of heat pump It “extracts” heat from inside and pumps it to the exterior. So, indoor you have cool air burning out of the vent, after passing through a heat exchanger. On the outdoor side you have warm air burning out of another heat exchanger. The heat exchanger on the indoor side is called an evaporator and the heat exchanger on the outdoor side is called a condenser.
Principles of Operation–
Stage 1 is the hot side heat exchanger (for air conditioning system this is on the outdoor side).
Stage 2 is the growth valve.
Stage 3 is the cold side heat exchanger (for air conditioning system this is on the indoor side).
Stage 4 is the compressor.
Decreasing heat pumps into these four stages is the primary methods by which to comprehend how heat pumps work.
Heat pump use a working fluid called a refrigerant. This refrigerant is selected based upon its helpful physical properties throughout the different stages of operation inside a heatpump. The refrigerant is distributed through the heat pump using a compressor, which owns the procedure. The refrigerant goes into the compressor, at phase 4, in a gaseous (saturated vapour) state at lower pressure and lower temperature level and exits at greater pressure and greater temperature level, in a superheated gaseous state. The refrigerant then goes through the hot side heat exchanger, and in so doing changes state into a liquid (stage 1). The associated heat loss of the gas and hidden heat of condensation (due to phase modification from gas to liquid) is moved out of the heat exchanger and into whatever medium the heat exchanger is in contact with. For a/c this medium is the outside air.
The refrigerant then travels through a growth valve (phase 2), which forces the liquid refrigerant to flash into a gas and liquid mix, at a pressure and temperature level both lower than prior to entering the valve. This mixture then passes through the cold side heat exchanger in phase 3, during which the refrigerant entirely converts into a gas. The associated hidden heat of vaporization (due to stage change of the liquid portion of the mixture into a gas) is absorbed by the heat exchanger from whatever medium the heat exchanger touches with. For air conditioning unit this medium is the indoor air. From this stage the refrigerant then goes into the compressor as a saturated vapour, and the cycle repeats.
As you can possibly see, the useful refrigerant properties are primarily phase modification residential or commercial properties, which happen spontaneously when the refrigerant goes through pressure and temperature modifications both in the compressor and expansion valve. To fully comprehend this procedure one must carry out a thermodynamic analysis.
One interesting element of how heat pump work is that you can really transport more heat energy than the energy needed to run them. For instance, with an ac system you can transport more heat energy from a structure than the electrical energy needed to power it. This makes it seem like there is an effectiveness of over 100%. However how is this possible? How can you get free ride? Well, you actually do not. As said previously, a heat pump simply transports energy from one place to another. This is not the very same thing as developing something out of absolutely nothing. So when it comes to a heat pump it ends up being better, for semantics if absolutely nothing else, to specify a Coefficient of Performance (COP), which is: (heat transferred)/ (energy input). So for an “effectiveness” of 400%, COP = 4.
Additionally, a heat pump can be used as a heating unit rather of a cooler/refrigerator. This is essentially taking an air conditioning unit and flipping it around; so that the outside part is facing indoors and the inside part is dealing with outdoors. With this set up you will have a heater instead of an a/c, and as soon as again, you can have an apparent performance higher than 100%.
In order to have a high COP, you need to be operating between particular temperature ranges. So if you are using a heat pump as a heater throughout the winter, you cannot have an outdoor temperature level that is excessively cold, otherwise your COP will decrease. In truth, the COP will approach 1 for outside temperatures that are -18 degrees Celsius or chillier. This is since it becomes significantly tough to draw out heat from the outdoors (to pump inside your home) the cooler it gets. Ultimately, the heat transferred becomes equivalent to the electrical energy input (COP = 1), and the cost of heating becomes far more expensive. So in this case a heat pump used for heating is best used during mild winter temperature levels.
Likewise, if you utilize a heat pump as a cooler (ac system) during the summer, you can not have an outdoor temperature that is exceedingly warm; otherwise your COP will decrease. Luckily, it never gets nearly hot enough throughout the summer season to lead to COP approaching 1– it would take an outdoor temperature of 50+ degrees Celsius!
This makes good sense intuitively– a lower COP is the result of “pushing heat uphill” to a higher degree, and working against the natural direction of heat transfer– which is from hot to cold. So the higher the temperature level distinction you are working versus, the more energy it takes and the less you get for your cash.