A microjet based recuperator for application in domestic micro chp

Abstract

Paper presented at the 8th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Mauritius, 11-13 July, 2011.

In the paper the original design of a compact heat exchanger with microjets producing intensification effect is presented. Its primary application is for the domestic Organic Rankine Cycle (ORC), however, the design is universal and may have numerous other applications. The technology of microjets manufacturing is an “in-house” patented design. In the present paper the idea of such a heat exchanger is shown together with the flow and thermal characteristics of the prototype. The developed prototype of heat exchanger is capable of exchanging 5 kW of thermal energy at a logarithmic mean temperature difference (LMTD) of 60 K. The total heat transfer surface equal to 0.0072 m2 leads to very significant heat fluxes. Measured overall heat transfer coefficient reaches 12000 W/m2K, which was calculated using the Wilson method. The description of the Wilson technique used for the determination of the heat transfer coefficient is also presented in the body of the text. That method seems to be, in the authors’ opinion, the only one for finding the heat transfer coefficient for such a complex heat exchanger structure. In this case measurements of wall temperatures are not possible and hence the determination of heat transfer coefficient is difficult. The results of performed measurements are satisfactory and encourage for further research of the original design.