The role of heat pipes in intensified unit operations

Heat pipes are heat transfer devices that rely, most commonly, on the evaporation and condensation of a working fluid contained within them, with passive pumping of the condensate back to the evaporator. They are sometimes referred to as ‘thermal superconductors’ because of their exceptionally high effective thermal conductivity (substantially higher than any metal). This, together with several other characteristics make them attractive to a range of intensified unit operations, particularly reactors. The majority of modern computers deploy heat pipes for cooling of the CPU.
The application areas of heat pipes come within a number of broad groups, each of which describes a property of the heat pipe. The ones particularly relevant to chemical reactors are:
i. Separation of heat source and sink.
ii. Temperature flattening, or isothermalisation.
iii. Temperature control.
Chemical reactors, as a heat pipe application area, highlight the benefits of the heat pipe based on isothermalisation/temperature flattening device and on being a highly effective heat transfer unit. Temperature control, done passively, is also of relevance. Heat pipe technology offers a number of potential benefits to reactor performance and operation. The aim of increased yield of high purity, high added value chemicals means less waste and higher profitability. Other intensified unit operations, such as those employing sorption processes, can also profit from heat pipe technology.
This paper describes several variants of heat pipe and the opportunities for their use in intensified plant, and will give some current examples.

The work is being consolidated into PhD studies involving the use of renewable energy to drive chemical reactions with heat transport between the RE source and the reactor being via heat pipes. These are compatible with the highest temperature solar concentrators and will use the isothermalisation feature of the heat pipe, as well as heat flux transformation. Professor Reay is a leading expert in heat pipes and is co-author (initially with Prof. Dunn of Reading University and latterly with Dr. Kew of Heriot-Watt University) of the standard text on the topic, entering its 6th Edition.