Effect of relative humidity on thermal conductivity of zeolite-based adsorbents: Theory and experiments

Effective thermal conductivity (ETC) of the adsorbent is an important parameter which influences the performance of the adsorption heat pump and adsorption cooling systems. Most of the adsorbents are porous in nature and therefore adsorption uptake is affected due to different operating conditions i.e. temperature and relative humidity (RH) that result in different ETC. Effect of temperature on ETC is somehow well-known in the literature, however, studies on RH effect are limited. Therefore, present study experimentally investigates the RH effect on the thermal conductivity of the commercially available zeolite-based adsorbents which are traded as: AQSOA-Z02 (zeolite-1) and AQSOA-Z05 (zeolite-2). The study is useful for the researcher who are working in the field of adsorption cooling, air-conditioning and desalination. In this regard, an experimental setup was developed by which the ETC was measured at different levels of RH. According to the results, the ETC of oven dried zeolite-1 and zeolite-2 was 0.060 W m⁻¹ K⁻¹ and 0.066 W m⁻¹ K⁻¹, respectively. With the increase in RH, the value of ETC increases up to 0.090 W m⁻¹ K⁻¹ for zeolite-1 and 0.089 W m⁻¹ K⁻¹ for zeolite-2. Moreover, an empirical relation is proposed which can estimate ETC at different levels of RH for both adsorbents.