Laboratory for Refrigeration and Heat Pumps – STET

Laboratory for Refrigeration and Heat Pumps

Heat pump/chiller using minichannel heat exchangers


View of the heat pump with the safety fans and the casing for instrumentation.
The use of hydrocarbons is a good opportunity to develop environmentally friendly HVAC equipment, since the direct effect of the refrigerant on the anthropogenic global warming is almost completely avoided, while the indirect effect can be reduced by exploiting the favorable thermodynamic properties of these fluids.

In the case of large systems for heating and cooling of buildings, such equipment could be situated in a machinery room or outside in the open air (for example on the roof of the building) in order to provide some kind of intrinsic safety.


The charge inventory minimization is a major design objective for equipment using flammable fluids like hydrocarbons. The same restriction should be adopted also in systems operating with halogenated fluids or when using other refrigerants with some degree of toxicity. Minichannels technology appears to be a very good opportunity to further minimize the charge without loss in energy performance.
View of the heat pump with prototype of evaporator.


Heat pump facility.


Tube bundle in the minichannel condenser
The present unit, a water-to-water heat pump, has been designed for testing applications and five heat exchangers have been installed: two commercial plate heat exchangers (PHEs) can be used as an evaporator and a condenser, while prototypes heat exchangers using minichannels can be used as a condenser, an evaporator and an internal heat exchanger (IHX).

The heat pump has been situated outside in the open air on the roof terrace of Department of Ingegneria Industriale building.


Tube bundle in the minichannel heat exchanger details