DK-heat pump storange tank

Three versions
1. heating & cooling
2. heating
3. heating &mains water warming in one tank
Main application areas
Stores with Heat exchanger for heating water air heater (warm & cold water)
Bigger stores with heating through air to air heat pump and additional heat exchanger for heating water for office, side rooms and door curtains.
Private houses

General description of an air / water heat pump:

Finned tube exchanger will be used as heat exchanger for all three systems. The reason for that version is the robustness of the finned tube exchanger, which is very important when the heat pump is running - especially by air to water heat pumps.

Air / water heat pumps are equipped with a so-called hot gas defrosting.

At outside temperatures around zero degree and simultaneous high humidity the evaporation temperature is below zero and this leads to freezing of the outside evaporator.

All air / water heat pumps therefore are equipped with a hot gas defrosting based on a reverse circuit.

The hot gas flows through the evaporator to defrost it.

Each hour this defrosting period takes a few minutes at 100 % compressor performance.

If a usual plate heat exchanger is used, due to its low water content, this could freeze and burst.

So a working pump is the live insurance for every plate heat exchanger.

If there is now flow the heat exchanger cracks and water flows into the refrigerant circuit.

This causes a total breakdown of the plant.

DK-Heat Pump Storage Tank cannot freeze over because the finned tube heat exchanger are inside the buffer tank

  • There a sufficient amount of thermal energy for defrosting is always present even without a pump by above freezing temperature.

The refrigerant content mostly is higher than 2,5 kg so it is required to install a low pressure switch as well a high pressure switch.

A heating loop usually works with a maximum operation pressure of 3 bar. Some heat pumps are equipped with a low-pressure switch that cuts off the plant at 1 bar. So in case of a damage the danger of a water inflow is very high.

Coiled fin tube heat exchanger as an ultimate solution

We modified the well-known coiled fin tube heat exchangers particular for this application. The robustness of this heat exchanger is very important for heat pump applications. Thus DK can guarantee that the heat exchanger will not be damaged by freezing-up.

Heating & Cooling

Main area of application:

Stores with Heat exchanger for heating water air heater (warm and cold water)


  • Tank with switchable internal heat exchanger for heating and cooling
  • Heat exchanger are equipped with venturi multi-injunction on the cooling side (fluid connection)
  • Interconnection to a common connection (hot/suction gas)

During cooling:

  • The refrigerant is flowing from bottom to top
  • Liquid IN via venturi multi-injunction and electrical expansion valve
  • Suction gas OUT on top

During heating:

  • The refrigerant is flowing from top to bottom
  • Hot gas IN on top
  • Liquid OUT via venturi multi-injunction

The electrical valve assumes the function:

  • of the electrical expansion valve during cooling
  • of the condensing pressure regulator during heating

Periods of defrosting

  • For defrosting and for an oil return (inversion of cooling circuit)

The heat exchanger inside the tank are working now as an evaporator. The heat exchanger (finned tube exchanger) can tolerate ice deposit.


Main area of application:

Bigger stores with heating through air to air heat pump and additional heat exchanger for heating water for office, side rooms and door curtains.

Heating & mains water warming in one tank

  • additional connection options for solar and other heating sources
  • bivalent operation possible with either existing gas or oil-fi red heating system
  • standard vessel sizes: 450 and 750 l; other capacities available upon request with integrated water heater (125 / 240 l) as storage tank or as continuous-flow water heater or


Calculation for heat exchanger with Qo = cooling