Experimental study of a dual condenser (EVACON) with concentric helicoids in use with an absorption heat transformer

Abstract

The purpose of the present work is the experimental characterization of an innovative dual condenser (performing two unitary operations under a single shell) with nested helicoids and obtain the experimental overall heat coefficient that can be used in the future for designers. The device was designed, characterized, and experimentally tested, ready to be adapted into an absorption heat transformer on a pilot scale of 5000 W of heat capacity. The internal geometry of the condenser consists of 7 concentric coils, nested in a rigid shell and connected in parallel through a manifold that distributes the service fluid into the coils. The steam from the evaporator condenses on the outside of the tubes creating a uniform falling film. The construction material is 304 stainless in order to secure a prolonged service life. The experimental evaluation consisted of 24 experimental tests that were carried out using water as a working and service fluid at 4 different temperatures and 6 different feed flow rates from the source. The study consisted of determining the heat capacity rate of the condenser as well as its heat transfer coefficient. The heat capacity rate was calculated using an energy balance in the dual device. We used correlations to helicoidally geometry to determine the overall heat transfer and convective heat coefficients. The sizing method was validated taking into account the theoretical and experimental overall heat transfer coefficient of 678 W/m2 K.The results show the maximum heat capacity of the condenser at 4179 W. The overall heat transfer coefficient varies between 441 and 614 W/m2°C, while the convective heat transfer coefficient for condensation (film side) ranges between 1288 and 1615 W/m2°C. These values are higher than those previously reported for similar coil heat exchangers in similar operation conditions. These results let us know that the condenser will have a good performance when adapted into a heat absorption machine.