Heat Pump

Triple effect machine with solid and liquid absorber

The aim of this project, run by the "Bavarian Centre for Applied Energy Research" (ZAE) is to construct a prototype heat pump / chiller powered by heat. The aim is for this to have a significantly better heat ratio, i.e. better fuel utilisation, than current conventional machines. 

Summary

Sorption chillers represent both an environmentally friendly and energy efficient technology for solar cooling.

In this context, the aim of the project is to construct a prototype heat pump / chiller powered by heat. The aim is for this to have a significantly better heat ratio, i.e. better fuel utilisation, than current conventional machines.

To achieve the project's objective, the part load behaviour of a two-stage liquid sorption chiller was studied with water as the refrigerant and water  lithium bromide as the sorbent. As the next stage, this so-called double effect system was then linked to a gas/solid system (chemical heat pump) with ammonia as the refrigerant and nickel chloride ammonia as the sorbent to create a triple effect system. No integration of substances between the two sorption refrigerating systems was possible as different refrigerants were used. Thus, the triple effect system was implemented as a combination of all external heat exchangers in the two individual systems, resulting in an overall system which, from an external perspective, behaves in the same way as a system with driving heat, cold water and cooling water.

The experiments focused on studying the operating and control behaviour, as well as the efficiency of the overall system.

Results:

  • The triple effect system created was only just able to exceed the circuit COP (coefficient of performance) of the double effect system. However, in principle there is still potential for this to be increased.
  • A different circuit can be used to avoid the weaknesses of the circuit created.  For example, the problem of asymmetry can be resolved by a topping cycle, whose condenser waste heat can also be utilised.  Alternatively, a pair of substances can be used that has a lower relative difference in specific heat capacity (per mole of refrigerant converted) between the charged and uncharged sorbent.

More Project Informations

Project number:  0326962A0

Project period:  1995 - 2000

Project region:  Germany (Bavaria)

Project contact:

Berlitz

View Publication

Source: German National Library of Science and Technology Hannover (TIB)