Bjorn Nienborg[12]*, Stefan Gschwander1, Li Huang[13], Peter Schossig1
1 Fraunhofer Institute for Solar Energy Systems, Heidenhofstr. 2, 79110 Freiburg, GERMANY
2 Fraunhofer Institute for Environmental-, Safety — and Energy Technologies, Osterfelder Str. 3, 46047

Oberhausen

* Bjoern. Nienborg@ise. fraunhofer. de

Phase change materials (PCM) offer a great potential for energy saving in heating and cooling applications as well as efficient energy storage. A series of solid materials has come into the market during the last years. Phase Change Slurries (PCS) are mixtures of a Phase Change Material and a carrier fluid so the material can be pumped. At Fraunhofer Institute for Solar Energy Systems (ISE) two types of PCS are investigated: emulsions and suspensions.

As PCS compete with water which is usually used as pumpable heat transfer medium, they need to meet a multitude of requirements in order to compensate the higher investment cost by lower operation expenses.

At our institute the materials can be analyzed on small scale in a laboratory. Once a promising product is detected, it is tested in a testing facility which reproduces reality-like operation. This work describes the testing facility and illustrates the parameters that can be measured. Subsequently results of an example measurement of a phase change emulsion for cooling applications are presented.

Keywords: phase change material, PCM, Phase Change Slurry, PCS, thermal energy storage

these ice-slurries a large amount of energy can be transferred at 0 °C. For many applications e. g. building climatization with comfort temperatures of 22 °C — 24 °C, working with temperatures around the freezing point has a great disadvantage as they unnecessarily reduce the efficiency of the chiller [5]. For this reason Fraunhofer ISE is working on PCS on basis of paraffin with the melting point close to the targeted working temperature.

There are two types of PCS being investigated:

— Emulsions with the dispersed paraffin mixed directly with water and emulsifiers preventing the accumulation of the paraffin drops.

— Suspensions of microencapsulated paraffin with the shell preventing an interaction of the paraffin with the water.

A testing facility for PCS has been set up at Fraunhofer ISE, which allows the analysis of their physical properties and the suitability for the designated use.