Calculation of heat pumps

Heat pumps are becoming a popular option for effectively and sustainably heating your home. Heat pumps, in contrast to conventional heating systems, move heat—even on chilly days—from the outside of a building inside. Because of their ability to provide both heating and cooling, heat pumps are a flexible choice for comfortable indoor temperatures all year round.

Understanding your unique heating requirements and how a heat pump works with the infrastructure of your current house are important factors to consider when selecting the best heat pump for your house. Selecting the proper heat pump size and model is essential for cost- and energy-effectiveness as well as for obtaining the highest level of comfort. Uneven heating or cooling, higher expenses, and increased energy consumption can result from an oversized or undersized unit.

Many factors need to be taken into account in order to choose the ideal heat pump for your house. These consist of your home’s dimensions and design, the climate where you live, and the degree of insulation in your home. An efficient solution to your heating and cooling needs is a heat pump system, which can be fully utilized with careful calculation and selection.

Methods and programs for calculating the heat pump capacity for home heating

Utilizing alternative energy sources appears to be a top concern in the modern world. Converting solar, wind, and water energy can save money by reducing pollution in the environment and avoiding the need to invest in expensive energy-generating technologies. The application of so-called heat pumps appears to be highly promising in this regard. An apparatus that transfers heat energy from the outside to the interior of a space is called a heat pump. The following contains the heat pump calculation method, required formulas, and coefficients.

Sources of thermal energy

Heat pumps can draw energy from the sun, air, water, and the earth. The method is based on the physical mechanism that allows some materials, or refrigerants, to boil at low temperatures. Heat pumps can have a coefficient of performance of three or even five units in such circumstances. This indicates that you can obtain 0.3–0.5 kW for every 100 W of electricity used to run the pump.

Therefore, as long as the outside temperature does not drop below the calculated level, the geothermal pump can effectively heat the entire house. How is a heat pump calculated?

Methods for figuring out a heat pump’s capacity

Either a dedicated online heat pump calculator or manual computations can be performed for this purpose. Ascertaining the house’s thermal balance is essential prior to calculating the pump capacity needed for manual heating. The same formula is applied regardless of the size of the house being calculated (heat pump calculation for 300m2 or 100m2).

• R is the heat loss/power of the house (kcal/hour);
• V – volume of the house (length*width*height), m3;
• T – the highest difference between the temperatures outside the house and inside in the cold season, C;
• k is the average heat conductivity coefficient of the building: k=3(4) – a house made of planks; k=2(3) – a house made of single-layer brick; k=1(2) – a brick house in two layers; k=0,6(1) – a thoroughly insulated building.

A typical heat pump calculation assumes that you must divide the obtained values by 860 in order to convert them from kcal/hour to kWh.

An example of how to figure out the pump capacity

Computation of a heat pump using a real-world example to heat a home. Assume for the moment that a structure measuring 100 m³ needs to be heated.

You must multiply its height by its length and width in order to get its volume (V):

Obtaining the temperature differential is required in order to determine T. In order to accomplish this, we deduct the minimum indoor and outdoor temperatures:

If we assume that the building’s heat losses are equal to k=1, the heat losses of the house can be computed as follows:

The heat pump calculation program makes the assumption that the household’s heat energy usage should be expressed in kilowatt-hours (kWhs). Let’s translate kcal/hr to kW:

Thus, a 14.5 kW heat pump is required to heat a 100 m³ home built of double-layer bricks. In the event that the heat pump for 300 m^2 needs to be calculated, the relevant substitution is made in the formulas. The amount of warm water needed for heating is factored into this computation. It is necessary to have a heat pump calculation table that illustrates the features and functionality of a specific model in order to choose the right heat pump.

The house’s heat balance must be ascertained prior to calculating the pump capacity needed for manual heating.

Heat pumps are known to operate on free and renewable energy sources, such as open, non-freezing water bodies, the low-potential heat of the earth, underground, waste, and discharge water from technological processes. Although electricity is consumed, the ratio of heat energy received to electric energy consumed is approximately 3:6.

More specifically, -10 to +15 °C outdoor air, 15 to 25 °C air discharged from the room, subsurface (4–10 °C) and ground (> 10 °C) water, lake and river water (0–10 °C), surface (0–10 °C), and deep (> 20 m) soil (10 °C) can all be sources of low-potential heat.

There are two ways to extract low-potential heat from the earth: vertical boreholes 20–100 meters deep, or trenches with metal–plastic pipes 1.2–1.5 meters deep. Pipes are occasionally installed in trenches that are 2-4 meters deep in the shape of spirals. This considerably shortens the trenches’ overall length. The surface soil can transfer between 50 and 70 kWh/m2 of heat per year. Trenches and boreholes have a service life of more than a century.

An illustration of a heat pump calculation

Initial requirements: The water in the heating system must be 35 °C, and the coolant must be at least 0 °C. A heat pump must be selected for the heating and hot water supply of a 200 m³ cottage two-story house. 50 W/m2 is the building’s heat loss. The ground is dry clay.

Heating requires the following heat power: 200*50=10 kW;

200 * 50 * 1.25 = 12.5 kW of heat capacity is needed for heating and hot water supply.

The heat pump WW H R P C 12, which has a capacity of 14,79 kW (the closest larger size), is selected for the building’s heating and uses 3,44 kW to heat freon. Heat transfer from the ground’s surface layer (dry clay) is 20 W/m. Compute:

1) the collector’s necessary heat capacity, Qo = 14,79 – 3,44 = 11,35 kW;

The total pipe length, L, is equal to Qo/q, or 11,35/0,020, or 567.5 м. Six circuits measuring 100 meters in length are needed to set up such a collector;

3) the necessary site area at A is 600 x 0.75 = 450 m^2, with a laying pitch of 0.75 m;

4) The glycol solution’s overall flow rate (25%)

Vs is equal to 11,35-3600/ (1,05-3,7-dt) = 3,506 m3/h.

A single circuit’s flow rate is 0,584 m3/h. dt, or the temperature differential between the supply and return lines, is commonly taken to be 3 K. We select a size 32 metal-plastic pipe (PE32x2, for example) as the collector. Its specifications include a 45 Pa/m pressure loss, a single circuit resistance of roughly 7 kPa, and a coolant flow velocity of 0.3 m/sec.

The horizontal heat pump collector calculation

Heat removal from each meter of pipe depends on many parameters: the depth of laying, the presence of groundwater, the quality of the soil, etc.д. It can be roughly assumed to be 20 W/m for horizontal collectors. More precisely: dry sand – 10, dry clay – 20, wet clay – 25, clay with a high water content – 35 W/m. The difference in temperature of the heat-carrier in the direct and return line of the loop is usually equal to 3 °С. No buildings should be erected on the area above the collector, so that the ground heat is replenished by solar radiation. The minimum distance between the laid pipes should be 0.7-0.8 m. The length of one trench is usually from 30 to 120 m. It is recommended to use a 25% glycol solution as the primary circuit coolant. In calculations it should be taken into account that its heat capacity at a temperature of 0 ° C is 3.7 kJ/(kg-K), density – 1.05 g/cm3. When using antifreeze, pressure losses in pipes are 1.5 times greater than when circulating water. To calculate the parameters of the primary circuit of the heat pump unit, it will be necessary to determine the flow rate of antifreeze:

Where t is the temperature differential between the return and supply lines, commonly assumed to be 3 K,

And Qo, or the heat power from ground, is the low-potential source’s heat power.

The final figure is computed as the difference between the electric power required to heat freon P and the heat pump’s total power, Qwp:

The following formulas are used to determine the total area under the collector pipe (A) and its length (L):

Here, da is the distance between pipes (laying step); q is the specific heat removal (from 1 m of pipe).

U-shaped metal-plastic or plastic (for diameters above 32 mm) pipes are submerged in vertical boreholes from 20 to 100 m in depth. Typically, a single well is filled with cement mortar after two loops have been inserted into it. It is reasonable to assume that such a probe has a specific heat input of 50 W/m on average. You may also consult the following information regarding heat removal:

* 20 W/m for dry sedimentary rocks;

* Water-saturated sedimentary rocks and stony soil – 50 W/m;

* a rock with 70 W/m of high thermal conductivity;

* The water table is 80 W/m.

The ground temperature at a depth of more than 15 m is constant and is approximately +10 °C. The distance between the wells should be more than 5 meters. If there are underground currents, the wells should be located on a line perpendicular to the flow. Selection of pipe diameters is carried out on the basis of pressure losses for the required flow rate of the heat carrier. The calculation of the liquid flow rate can be carried out for t = 5 °С. Calculation example. The initial data are the same as in the above calculation of the horizontal collector. If the specific heat input of the probe is 50 W/m and the required power is 11.35 kW, the length of the probe L should be 225 m. For the collector it is necessary to drill three boreholes 75 m deep each. In each of them we place two loops of metal-plastic pipe of size 25 (PE25x2).0); in total – 6 circuits of 150 m each.

The heat carrier’s overall flow rate at t = 5 °C will be 2.1 m3/h, and the flow rate through a single circuit will be 0.35 m3/h. The circuits will have the following hydraulic properties: flow velocity of 0.3 m/sec; circuit resistance of 14.4 kPa; heat carrier of 25% glycol solution; pressure loss in the pipe of 96 Pa/m.

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It’s important to precisely determine the size and capacity required for a heat pump installation when thinking about heating and insulation for homes. This can be done by taking into account variables like climate, home size, and insulation quality. Selecting the best heat pump requires knowing how efficient it is, which is usually determined by the coefficient of performance (COP), and making sure it can sufficiently meet heating demands in the winter months without requiring excessive energy expenditures. A well-calculated heat pump is a wise, environmentally friendly option for efficient home heating since it maximizes energy savings, reduces environmental impact, and improves comfort.

Heat pumps. Calculation, equipment selection, installation.

4.1. A heat pump’s working principle

Ukraine’s impending energy crisis can be avoided by using alternative, clean energy sources. A promising path is the utilization of energy stored in water bodies, ground, geothermal sources, and technological emissions (air, water, wastewater, etc.), in addition to the exploration and development of conventional sources (oil and gas). Nevertheless, these sources have a relatively low temperature (0–25 °C), so in order to use them effectively, the energy must be transferred to a higher temperature range (50–90 °C). Heat pumps (TH), which are actually vapor-compression refrigeration units, are responsible for achieving this conversion (Fig. 4.1).

The evaporator (3), where the refrigerant boils at a temperature of -10 °Ρ…+5 °Ρ, is heated by the low-temperature source (INT). Additionally, the traditional vapor-compression cycle transfers the heat to the refrigerant to the condenser (4), from where it is supplied to the consumer (HTP) at a higher level.

Heat pumps are used in various industries, residential and public sectors. At present there are more than 10 mln. heat pumps of different capacities: from tens of kilowatts to megawatts. Every year, the thermal pump fleet is replenished by about 1 million units. pieces. For example, in Stockholm, a heat pump station with a capacity of 320 MW, using sea water with a temperature of +4 ° C in winter, provides heat to the whole city [4]. In 2004. The capacity of heat pumps installed in Europe was 4,531 MW, and globally heat pumps produced heat energy equivalent to 1.81 billion. m 3 of natural gas. Heat pumps utilizing geothermal and groundwater are energy efficient. In the USA, federal legislation has approved requirements for the mandatory use of geothermal heat pumps (GHPs) in the construction of new public buildings. In Sweden, 50% of all heating is provided by geothermal heat pumps. By 2020. The World Energy Committee predicts that the share of geothermal heat pumps will be 75 %. The service life of GTN is 25-50 years. The prospectivity of heat pumps application in Ukraine is shown in [5].

Heat pumps are classified based on the type of heat transfer chain (source-consumer) and the operation principle (compressor, absorption). Different types of heat pumps are identified based on where the heat source is located first: air-air, air-water, water-air, water-water, ground-air, and ground-water. The system is referred to as monovalent if the heat pump is the only source of heating. A system is referred to as bivalent if it has a second heat source connected to it that can run either independently or in tandem with the heat pump.

Fig. 4.1: A hydronic heat pump’s schematic diagram

1 heat pump evaporator; 2 low level heat source (LLHS); 3 compressor;

High level heat consumer (HHW); 4-heat pump condenser; 5-

Heat exchanger with low temperature (6); refrigerant flow regulator (7);

8. A heat exchanger with a high temperature

A heat pump unit is a heat pump that has hydraulic piping (water pumps, heat exchangers, shut-off valves, etc.) 3. The mode of the TH can be switched to the reverse mode (cooling to heating and vice versa) by adjusting the flows of the media that are used to cool the evaporator and heat the condenser (water-water, air-air). This type of mode change is known as a reversible pneumatic cycle if the media are gases and a reversible hydraulic cycle if the media are liquids (Fig. 2). 4.2).

Heat pump scheme with reversible hydraulic cycle (Fig. 4.2).

The phrase "heat pump operating in a reversible refrigeration cycle" is used when the cycle’s reversibility is achieved by adjusting the refrigerant direction using a reversible cycle valve.

4.2. Low potential heat sources

4.2.1. The low potential source is air

Air-to-water heat pump scheme (Fig. 4.3)

Air conditioning systems frequently employ air-to-water heat pumps. The water used for space heating indoors is heated by the heat extracted from the condenser, which is blown through the evaporator with outside air (Fig. 4.3).

The availability of air, a low-potential heat source, is a benefit of these systems. Nonetheless, there is a wide range of variation in air temperature, with negative values. In this instance, the heat pump’s efficiency is significantly decreased. Thus, the heat pump’s performance drops by 1.5–2 times when the outside air temperature drops from 7 °C to minus 10 °C.

Heat exchangers, called "fan coils" in the literature, are installed in the heated rooms to supply water from the heat pump to them. The hydraulic system’s pumping station provides water to the fan coil (Fig. 4.4).

Fig. 4.4: Pumping station scheme:

RB stands for expansion tank, AB for accumulation tank, RP for flow switch, P for pressure gauges, and so on.

Balance valve (BC), filter (F), check valve (OK), valve (V), and thermometer (T);

TP stands for heat exchanger "freon-liquid," PC stands for safety valve, THC for three-way valve, CPF for liquid make-up valve, and CPV for air make-up valve. Air outlet valve, or AHV

Accumulation tanks are installed to lower the hydraulic system’s inertia and improve the accuracy of temperature maintenance in the space. According to formula [8], the accumulation tank’s capacity can be ascertained:

Where the heating system’s cooling capacity, expressed in kW;

– the cooled premises’ volume, measured in m³;

– is the system’s water content, l;

Z is the heat pump’s power stage count.

Should VAB The accumulation tank is not installed if the accumulation tank’s volume is negative.

Expansion tanks are installed in the hydraulic system to account for the thermal expansion of the water. On the pump’s suction side are installed expansion tanks. The expansion tank’s volume is calculated using the following formula [8]:

Where l is the system volume (Vsyst);

The liquid’s coefficient of volumetric expansion (k) is 3,7-10 -4 for water and 4,0-5,5)-10 -4 for antifreeze.

ΔT is the liquid’s temperature differential (only when in cooling mode).

When using the heat pump mode, ΔT equals 60 °C minus 4 °C, or 56 °C.

Upstream: Configuring the safety valve.

The mutual location of the pumping station and the end user (fan coil) determines the system pressure (Psyst). The pressure (Psystem), if the pump station is situated downstream of the final consumer, is equal to the maximum height difference (in bar) plus 0.3 bar. Psyst = 1.5 bar if the pumping station is situated above every consumer.

After installation, the expansion tank’s pressure is increased to its standard level after being pre-pressurized with air to a pressure that is 0.1–0.3 bar lower than the design pressure.

Fig. 4.5 depicts the expansion tank design.

IVIK.ua4.1 is the source. The emergence of an energy crisis in Ukraine can be avoided by using environmentally friendly alternative energy sources. A promising path is the utilization of energy stored in reservoirs, ground, geothermal sources, and technological emissions (air, water, sewage, etc.), in addition to the exploration and development of conventional sources (oil and gas). Nevertheless, these sources have relatively low temperatures (0–25 °C) and.

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Selecting the ideal heat pump for your house will not only maximize energy efficiency and reduce expenses, but also guarantee comfort. The procedure entails determining the precise heating and cooling needs of your area while taking the building’s size, insulation levels, and local climate into account. An appropriately sized heat pump will function effectively, lessening the burden on the device and possibly increasing its longevity.

It is important to choose the type of heat pump—air-source, ground-source, or water-source—that best meets your needs. Every type has advantages and disadvantages of its own, and the selection will have an immediate effect on installation costs and operational effectiveness. Having a professional evaluate the details of your house can help ensure more accurate calculations and customise a system to meet your financial and environmental objectives.

Furthermore, installing a good heat pump has advantages beyond financial savings and personal comfort. Heat pumps contribute to a more environmentally friendly and sustainable heating solution by lowering greenhouse gas emissions and dependence on non-renewable energy sources. Heat pumps play an ever-more-important part in sustainable home heating solutions as energy costs keep rising and environmental concerns get more urgent.

In the end, taking the time to determine which heat pump is best for your house will guarantee efficiency and comfort while also supporting larger environmental objectives. Through careful consideration of pertinent factors and expert consultation, homeowners can make well-informed decisions that maximize their personal space and support worldwide efforts to conserve energy.

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