Design and Development of Novel Desiccant Coated Fin Tube Heat Exchanger for Air Conditioning Application

Abstract

To improve indoor air quality, enhance the energy exchange capabilities, and minimize the spread of microbial pollutants, desiccant coated fin tube heat exchanger (DCFTHE) seem a promising alternative to conventional heat exchangers such as rotary wheel and adsorber beds due to their capability of decoupling the sensible and latent loads and utilizing low-grade thermal energy. The concept of desiccant coated fin tube heat exchangers can be employed in various heat exchange/transport systems like heat pumps, atmospheric water harvesters, adsorption chillers, and air conditioners. Thus, precise prediction of the design and performance characteristics of DCFTHE is vital for improving the overall performance of the air conditioning system. Therefore, two dynamic models based on the Laplace transform and finite difference approach are developed to assess the adsorption/desorption kinetics and thermal effects of DCFTHE. Lewis and Stanton numbers are chosen as the research parameters because they are significant in characterizing the coupled heat and mass transfer processes occurring across the air-desiccant interface. The interactive effect of the Lewis number and Stanton number on the performance parameters has been examined judiciously. Four different artificial intelligence/machine learning (AI/ML) models, namely adaptive neuro-fuzzy inference system (ANFIS), k-nearest neighbor (KNN), artificial neural network (ANN), and principal component analysis (PCA) have been developed to predict the exit parameters of DCFTHE and a physics-informed neural network (PINNs) based deep learning model has been established by integrating the underlying physical laws governing the energy and mass transport with the neural network. The optimal design/inlet conditions for the given operating and design parametric range of DCFTHE are obtained by employing the AI/ML approaches. A novel DCFTHE has been proposed, designed, and fabricated. Silica gel is used as the solid desiccant material. Experiments have been carried out to assess the moisture adsorption/desorption kinetics of the novel DCFTHE and evaluate the moisture uptake capability of the coated desiccant. The conjugate heat and mass transfer characteristics of the DCFTHE are experimentally examined. Phase change material (PCM) based thermal energy storage systems have evolved as a promising answer for effective thermal energy storage applications. Hence, the practicality of integrating PCM with DCFTHE for air conditioning and thermal energy storage necessitates experimental investigation. Thus, phase change material (paraffin wax) has been integrated with the novel DCFTHE to evaluate its dehumidification characteristics and the performance for thermal energy storage in its latent and sensible form. One of the key emphases of this research is the employment of PCM-Silica gel as a working pair instead of conventional Water-Silica gel. Two case studies have been carried out: first, a dehumidifier is integrated with an M-cooler/solar heater to evaluate the cooling/drying performance during dehumidification. Second, a thermal energy module is integrated with an industrial waste heat-driven DCFTHE during the regeneration process to assess the performance potentiality and energy storage capability of five different PCMs such as Climsel C48, Stearic acid, Myristic acid, n-hexadecane, and Palmitic acid, respectively. The influence of heating the regeneration heat transfer fluid via renewable energy sources on the performance of heat exchanger is examined. Silica gel's adsorption kinetics revealed that the maximum water uptake capability for the given operating range is 0.345 g.g-1. The case study shows that inlet cooling water temperature and inlet air temperature are the most significant parameters for the M-cooler and solar heater, which produce the lowest/highest temperature at the M-cooler/solar heater outlet, respectively. The effectiveness of thermal energy storage and the sensible energy efficacy ratio are maximum for Palmitic acid and minimum for Climsel C48, having corresponding values of 0.73/5.489 and 0.37/2.89, respectively. The significant findings of this research show that the developed dynamic models simplify the approach for assessing the DCFTHE transient performance and adsorption kinetics. The AI/ML approaches comprehended can be used for the design and performance prediction, analysis, and optimization of any heat exchanger. The proposed novel circular fin tube desiccant coated heat exchanger paves the way for the new design configuration of the desiccant coated fin tube heat exchangers.