The publications from this annex are:

  • A written full report detailing all information
  • An executive summary
  • A 2-page flyer

Reports are available at Annex 33 Publications.


The objective of this Annex was to present a compilation of possible options for compact heat exchangers, used as evaporators, condensers and in other roles in heat pumping equipment. The aim was to minimise the direct and indirect effect on the local and global environment due to operation of, and ultimate disposal of, the equipment.

Project manager and participating countries

United Kingdom was the Operating Agent acting through Brunel University. The following countries were participating: Austria, Japan, Sweden and the United States.


The activities included market research, the evaluation of the performance of compact heat exchangers relevant to heat pumps, the evaluation of properties and operating limits of such equipment, and information sharing. There was opportunities for open meetings at which industry and academia can put forward their views and contribute to the project.

The principal goal of the annex was to identify compact heat exchangers, either existing or under development, that may be applied in heat pumping equipment – including those using vapour compression, mechanical vapour recompression and absorption cycles. This had the aims of decreasing the working fluid inventory, minimising the environmental impact of system manufacture and disposal, and/or increasing the system performance during the equipment life.

A second goal was to identify, where necessary propose, and document reasonably accurate methods of predicting heat transfer, pressure drop and void fractions in these types of heat exchangers.

A third goal was to present listings of operating limits etc. for the different types of compact heat exchangers, e.g. maximum pressures, maximum temperatures, material compatibility, minimum diameters, etc. and of estimated manufacturing costs or possible market prices in large scale production.

The four partners contributed information from their countries and companies/institutions, and the Annex delivered data that would allow heat pump designers/manufacturers and users to take full benefits from the opportunities afforded by CHEs.