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The reversible heat pump

To realize an optimized air-cooled heat pump, Keyter Intarcon Nederland B.V., Keyter Technologies, S.L. and the Danish partner Klimalux have shared their knowledge and put their hand together. The result is an inventive heat pump that performs good at temperatures around 0°C with relative high humidity, but also at very low outside temperatures (around -20°C).

 

The idea of this development started when governments in most of the northern part of Europe (The Netherlands and Scandinavia) obliged companies to build gas-free. The developed Keyter KWK heat pump has put real emphasis on heating during design and development. There is not only a four-way reversing valve and neither a defrost cycle added to the standard chiller. But it also anticipates on the strict laws in these countries in order to attempt to keep refrigerant content of the individual refrigerant circuits circuits as small and short as possible. Fior example, most of these KWK units meet the Scandinavian requirements of 10 kg max. per circuit.

No more varying temperatures

The machine is built up with several small systems, not only to keep the refrigerant content small, but also to guarantee a constant (high) water temperature. Even at low outdoor temperatures around -20°C.

 

By using several (small) systems, the lowering of the water temperature during the defrost cycle is absorbed and the user will no longer experience varying temperatures (something which now occurs with standard heat pumps when only one circuit requires defrosting).

Meet the environmental requirements

We also deliberately opted for batteries with a greater distance between the fins, in order to prevent the freezing of it. But also if there is a need for defrosting, you will be able to manage it as quickly as possible. The chosen air-cooled batteries are also specially designed and adapted for heat processing, in cooperation with the experience and knowledge of the cooling and freezing technology of Intarcon.

 

This in combination with the integration of two fans per circuit (instead of one with the standard chiller of the same capacity) with an EBM PAPST AXITOP, to optimize the airflow and still keep the noise level as low as possible to meet the environmental requirements. With all these modifications, the evaporation temperature at low external temperatures remains within the limits of the compressor.

The graph of the special heat pump compressor compared to a standard cooling compressor

Heating mode

In heating mode, the air goes counter-currently to the refrigerant, which results in a better return during heating operation, which is nevertheless the focus of the heat pumps in the North European countries.

 

The individual systems will never thaw at the same time and the energy that is withdrawn from the water system, in order for the defrost to take place correctly, will be compensated by the other systems. These will absorb the drop in the water outlet temperature and thus maintain a constant (high) water outlet temperature from the heat pump.

 

But even during the cooling period, this heat pump still works perfectly well. By using well-selected batteries, up to 45°C external air temperature, it can still be transferred to the outside air with a good return.

 

In order to be able to supply a high water temperature at much lower outside air temperatures, the standard cooling compressor has been discontinued and special heat pump compressors have been used. These are designed to be able to run with both low evaporation and high condensation temperatures, so it won’t gets reduced in capacity when the outdoor air conditions are below -10°C. Something that is necessary when standard “cool” compressors are used.

Stable water temperature

The regulation of the KWK heat pumps has been carefully adapted by Keyter Technologies, S.L. to these components and therefore a high efficiency, stable water temperature and complete operational reliability can be guaranteed, regardless of the changing external conditions.

 

The electrical compartment (switch box) is physically separated from the compressor compartment. This is a result of which the electrical and electronic components do not become unnecessarily hot due to the heat of the compressor and the switching part is also equipped with temperature-controlled cabinet ventilation and cabinet heating.

 

The compressors are mounted vibration-free in an insulated acoustic compartment and also equipped with acoustic compressor covers, to keep the noise production (nuisance) as low as possible.

Multiple condenser fans with AXITOP diffuser, so that they do not have to run at full speed with decreasing or rising outside air temperature.

 

In order to prevent compressor damage due to liquid, especially after the defrosting cycle, when the refrigerant has accumulated in the air-cooled battery and reverses the cycle, all Keyter heat pumps are equipped with a suction gas liquid separator.

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