D.B. Jani

A Critical Review on Solid Desiccant-Based Hybrid Cooling Systems

The present review provides scientific and technical support on how solid desiccant-based hybrid cooling can be a supplement to the commonly used vapor compression-based traditional air-conditioning systems to provide the indoor thermal comfort to the occupants. The existing design of standalone vapor compression system needs to be modified by integrating it with the solid desiccant-based dehumidification system to achieve better performance and economic feasibility by handling humidity and temperature separately especially in case of hot humid conditions. The present study is undertaken by considering variety of aspects including background and need for alternative cooling systems, system configuration as well as operational modes and current status of desiccant-based hybrid cooling technology. The review work also indicates that the technology of desiccant-based hybrid cooling has a great potential to provide thermal comfort especially in hot humid climate at the expense of lower energy consumption as compared to traditional cooling systems.

Performance analysis of hybrid solid desiccant–vapor compression air conditioning system in hot and humid weather of India

The performance of hybrid solid desiccant–vapor compression air conditioning system is studied for the typical hot and humid climatic zone of North India (Roorkee). The system consists of a rotary desiccant dehumidifier coupled with heat recovery wheel and a conventional vapor compression air conditioning system. A FORTRAN program was developed to calculate different psychrometric properties like humidity ratio, dry-bulb temperature, wet-bulb temperature, relative humidity, specific heat, etc. at each state point of the system on the basis of ambient and desired inside room conditions, room cooling load, sensible heat factor, and required air flow rate. The overall system performance has been evaluated in terms of the coefficient of performance and the dehumidifier effectiveness. The influence of variation in ambient conditions on regeneration temperature of desiccants has also been discussed. The simulated results are validated using experimental measurements. The present system has ensured a reduction of 79.15% in processing air humidity ratio at an outlet of the desiccant dehumidifier as compared to the outdoor humidity ratio. The results show that the performance of the system is significantly affected by the variations in ambient temperature and humidity ratio. Practical application : The proposed model of solid desiccant–VCR hybrid air conditioning system minimizes the energy usage in comfort cooling applications such as auditoriums, supermarket, hospitals, central library, offices, and lecture halls in hot and humid climate while maintaining an acceptable thermal comfort level and improving the performance. The proposed approach will give valuable insights to the researchers and building engineers to analyze the impacts of ambient conditions on the energy requirements and performance of solid desiccant cooling to ameliorate comfort, energy, and cost savings. Moreover, its potential contribution in environmental protection makes it more attractive at a time where depletion of energy resources and environmental degradation are of major concerns.

Exergy analysis of solid desiccant-vapour compression hybrid air conditioning system

This paper presents energy and exergy analysis of a solid desiccant vapour compression hybrid air conditioning system. Parametric study has been conducted at varying dead state properties and operating conditions to investigate their effects on the overall system performance. The obtained results show that the exergy efficiency of hybrid air conditioning system is 11.45%. The energy-based performance parameters such as the coefficient of performance (COP) and components effectiveness are also presented. The rotary desiccant dehumidifier and heater are found as major contributors to exergy performance of the system. The analysis provides us beneficial knowledge to determine theoretical upper limit of the system performance.

Solar Assisted Solid Desiccant—Vapor Compression Hybrid Air-Conditioning System

Solar assisted solid desiccant—vapor compression based hybrid space cooling system for building thermal comfort is made by integrating desiccant based dehumidification system as well as by use of solar heating system along with conventional VCR system. This is because in humid climates, excessive humidity during summer leading to inefficiencies of conventional cooling devices. Humidity increment in ambient air as well as ventilation requirement suddenly rises the latent load of the space to be cooled. Conventional VCR systems are not effective in handling both temperature and relative humidity of cooling air independently. The application of solid desiccant based hybrid cooling systems significantly ameliorates the humidity control irrespective of temperature of supply air. The application of renewable free energy like as use of solar energy for regenerating the desiccant used in desiccant wheel helps us to alleviate the major requirement of electric energy needed by conventional VCR air-conditioning system for hot sunny days. So, it ameliorates overall energy efficiency and reduces energy costs. Performance of solid desiccant—vapor compression based hybrid building space comfort cooling system has been evaluated during hot and humid period from April to September for the ambient conditions of the Roorkee for various important parameters such as temperatures of supply air, room air and regeneration air etc. Regeneration temperature is one of the most important parameters having the key role in changing the performance of desiccant based cooling system.