DESIGNS OF HEAT EXCHANGER DEVICES ON TWO-PHASE HEAT TRANSFER ELEMENTS FOR AIR HEAT DISPOSAL IN VENTILATION SYSTEMS: OVERVIEW

Background. Heat exchangers-utilizers for recovery of ventilation air heat are widely used for increasing of buildings energy efficiency. Two-phase elements, such as: thermosyphons, heat pipes and pulsating heat pipes are applied to these heat exchangers for increasing of efficiency of heat transfer between hot and cold air. But such heat exchangers should have high temperature efficiency, enthalpy efficiency and energy efficiency at low aerodynamic drag. Moreover, working conditions of ventilation systems, such as: relatively low working temperatures and low temperature difference between hot and cold air, make it difficult to choose heat carriers for two-phase elements. Thus, it is necessary to solve a number of complex problems for designing of effective heat exchangers-utilizers based on two-phase elements. Objective. To find out unresolved and understudied issues of designing of heat exchangers-utilizers based on two-phase elements for ventilation systems. Methods. Analysis of described in literature designs, their characteristics and results of investigations. Results. General features of two-phase elements based heat exchangers-utilizers designs and a number of issues which need further investigation were detected as a result of literature sources analysis. Conclusions. Heat exchangers based on two-phase heat transfer elements have wide perspective of applying and provide full heat efficiency up to 85%. But there is a number of unsolved issues connected with: optimization of two-phase elements and heat exchangers design, ribbing optimization, investigation of heat transfer intensity and heat transfer coefficients, investigation of aerodynamic drag, condensate rejecting.