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Vapor chambers and heat pipes are often used as standalone heat spreaders for electronics cooling and in other applications. Metal additive manufacturing (AM) techniques have an intrinsic ability to form the porous structures and internal cavities required to fabricate a vapor chamber or a heat pipe. Additive manufacturing techniques thereby have potential for fabricating vapor chambers with complex geometries and locally tailored wick structures to improve performance as well as to monolithically embed vapor chamber heat spreaders within other components. The focus of the present work is to conduct an experimental assessment of the viability of additively manufactured vapor chambers. A direct metal laser sintering (DMLS) technique was used to fabricate a monolithic stainless steel vapor chamber heat spreader with a 39% porous, 0.5-mm thick wick and a 1.5-mm thick internal vapor core. The functionality of the as-printed vapor chamber was evaluated based on characterization of the heat spreading behavior with and without fluid charge. Charging with water decreased the effective thermal resistance of the device while spreading heat from a central hot spot, confirming functionality of the additively manufactured vapor chamber.

Air conditioning and refrigeration systems account for almost half of the energy consumption in buildings of the developed countries. The liquid sorption system is a promising alternative to the conventional vapor compression system which is energy inefficient. It is classified into open (dehumidification) and closed (absorption) systems which are used to control the humidity of air and temperature of the cooling stream respectively. The present study proposes a new hybrid system that integrates the absorption refrigeration system with a membrane dehumidifier for air conditioning and refrigeration. The proposed system also produces potable water from ambient humidity. It is viable only with the membrane dehumidifier since its microporous membrane avoids the direct contact between the air and solution streams but allows heat and mass transfer between them. As a result, the vacuum pressure of the proposed system remains unaltered. Moreover, the corrosion in the proposed (due to traces of air) and air handling systems (due to traces of solution) is avoided. In the present study, the performance of the proposed system is compared with the conventional absorption refrigeration system and also investigated under the influence of the design and operating parameters, and ambient conditions. Performance analysis found that the proposed system produces the air with 2.6 kW cooling capacity and 0.00102 kg/s potable water from the given evaporator load of 10 kW for the hot and humid climatic conditions.

Air conditioning (AC) systems demand a significant portion of the total energy consumed by the building sector. Conventional AC based on vapor compression refrigeration (VCR) is neither energy efficient nor environment-friendly due to its method of humidity control and use of refrigerants with global warming potential respectively. Liquid desiccant air conditioning system (LDAS) is a promising alternative to VCR. This review provides a comprehensive overview of the developments in LDAS so far. It explains the principle of operation and classification in detail. The various developments in dehumidifier, regenerator, desiccant material, and mathematical modelling are discussed. The various types of performance parameters, and the design criteria and effect of operating parameters are also detailed. Finally, the climate feasibility, performance control strategies and indoor air quality are explained. This communication will be useful to identify the research gaps to explore new pathways for future research to further improve the efficiency of LDAS.