K. Sumathy

Technology development in the solar absorption air-conditioning systems

An environmental control system utilizing solar energy would generally be more cost-effective if it were used to provide both heating and cooling requirements in the building it serves. Various solar powered heating systems have been tested extensively, but solar powered air-conditioners have received little more than short-term demonstration attention. This paper reviews past efforts in the field of solar powered air-conditioning systems with the absorption pair of lithium bromide and water. A number of attempts have been made by researchers to improve the performance of the solar applied air-conditioning (chiller) subsystems. It is seen that the generator inlet temperature of the chiller is the most important parameter in the design and fabrication of a solar powered air-conditioning system. While collector choice, system design and arrangement are other impacting factors for the system operation.

Solar absorption cooling with low grade heat source: A strategy of development in South China

Abstract Based on experiences with an operating solar cooling system in south China, a low temperature driven solar cooling system has been proposed, and a new model of two-stage lithium bromide absorption chiller has been developed. Test results have proved that the two-stage chiller could be driven by low temperature hot water ranging from 60 to 75°C, which can be easily provided by conventional solar hot water systems. Relying on the successes of the above system, an integrated solar cooling and heating system with two-stage absorption chiller was constructed (cooling capacity=100xa0kW). Preliminary operating data of the system has indicated that this type of system could be efficient and cost effective. Compared to the conventional cooling system (with single-stage chiller), the proposed system with a two-stage chiller could achieve roughly the same total COP as of the conventional system with a cost reduction of about 50%.

Experimental studies on a solar powered air conditioning system with partitioned hot water storage tank

Abstract This paper reports on the performance of a solar powered absorption air conditioning system with a partitioned hot water storage tank. The system employs a flat-plate collector array with a surface area of 38 m2 to drive a LiBr–H2O absorption chiller of 4.7 kW cooling capacity. The system is provided with a storage tank (2.75 m3) which is partitioned into two parts. The upper part has a volume of about one-fourth of the entire tank. The performance of this modified system is presented and compared with the conventional system design (whole-tank mode). The study reveals that the solar cooling effect can be realized nearly 2 h earlier for the system operating in partitioned mode. In this system a total solar cooling COPsystem of about 0.07, which is about 15% higher than with traditional whole-tank mode, is attained. Experimental results also show that during cloudy days, the system could not provide a cooling effect, when operated conventionally, however in the partitioned mode-driven system the chiller could be energized, using solar energy as the only heat source.

Theoretical study on a cross-flow direct evaporative cooler using honeycomb paper as packing material

A cross-flow direct evaporative cooler, in which the wet durable honeycomb paper constitutes as the packing material, is investigated. The system is expected to act as both humidifier and evaporative cooler to create a comfortable indoor environment in arid regions. A mathematical model, including the governing equations of liquid film and gas phases as well as the interface conditions, has been developed. The interface temperature of falling film has been predicted and discussed in detail. Analysis results indicate that there exists an optimum length of the air channel, which results in the lowest temperature, and the system performance can be further improved by optimizing the operation parameters, such as the mass flow rates of feed water and process air, as well as the different dimensions of the honeycomb paper.

Solar transparent insulation materials: a review

This paper presents a status report on solar transparent insulation materials (TIM). It covers a survey of the literature, various physical and other properties of TIM devices, their classifications, applications, fabrication procedures, availability and cost trends. The global resurgence of research is clarified. Subsequently, the development of TIM cover systems (often referred to as advanced glazing) from such products as polymer sheets, capillaries and cellular profiles, is discussed. Their design and performance characteristics are investigated; results corresponding to experimental measurements, as well as computational models, are presented. An explicit comparative study of absorber parallel and absorber perpendicular configurations of TIM cover systems is presented. The TIM covers with black end cover plates, and cellular walls of high emissivity, as well as those with selective cover plates and cellular walls fully transparent to IR radiations, have relatively lower heat loss coefficients.

Review of mathematical investigation on the closed adsorption heat pump and cooling systems

A mathematical model of the closed adsorption heat pump and cooling systems is particularly used to assist in interpreting the observed phenomena, to design the system, to predict the trends, and to assist in optimization. In this paper, various mathematical models mainly analyzing the heat and mass transfer process of an adsorption bed in closed adsorption heat pump and cooling systems are reviewed and classified based on complexity, into three main groups: i.e. thermodynamic model; lumped parameters model; heat and mass transfer model. The major characteristics of different models and assumptions used are presented and discussed. Also, the numerical methods and validation of the models are summarized and significant results obtained through mathematical model are detailed. Although the models have evolved to a point where several features of the process can be predicted, more effort is required before the models can be applied to define actual operating conditions as well as to further investigate new closed adsorption cycles.

A solar-powered ice-maker with the solid adsorption pair of activated carbon and methanol

This paper presents the description and operation of a solar-powered ice-maker with the solid adsorption pair of activated carbon and methanol. A domestic type of charcoal was chosen as the adsorbent, and a simple flat-plate collector with an exposed area of 0.92 m2 was employed to produce ice of about 4–5 kg d−1 at an evaporator temperature of about −6°C. The above system could achieve solar refrigeration COP of about 0·1–0·12. With the description of the idealized refrigerating system, the influences of evaporating temperature, adsorbing temperature and condensing temperature on the COP were also analysed. Copyright

Performance study of a partitioned thermally stratified storage tank in a solar powered absorption air conditioning system

Accurate modeling of solar heating or cooling with storage generally requires an accounting of the stratification within such storage tank, since overall system performance is significantly affected by the storage temperature distribution. In this study, a simple one-dimensional multi-node approach, taking into account of the axial heat conduction between nodes, has been used to theoretically analyze temperature stratification in the thermal storage tank. The results indicate that, for less collector area, the heat removal factor plays a major role in increasing the system performance, than the thermal stratification. Also, an optimum ratio of tank volume over collector area exists for a solar powered absorption air conditioning system. This paper also reviews the state of the art on different kinds of variable inlet design, and a simple new inlet design (partitioning the tank) has been introduced to effect better thermal stratification in storage tank.

Experimental Study on a Hybrid Desiccant Dehumidification and Air Conditioning System

This paper presents the experimental tests on hybrid desiccant dehumidification and air conditioning systems. Experimental tests are carried out with LiC1 desiccant at typical operative ranges for air conditioning applications, particularly for high humid regions like Hong Kong. Results are reported in terms of coefficient of performance (COP) based on primary energy usage and electrical energy usage, respectively. Experiments have demonstrated consistent reduction in humidity ratio satisfying the sensible as well as latent load through a respective subsystem and thereby resulting in a higher COP based on primary energy usage. Also, results show that the regeneration temperature as well as process air flow rate have a significant role on the system performance. It is found that the hybrid system can achieve a higher part load performance, and hence can assure of its effective operation all year around in hot humid regions.

Enhancement of natural ventilation in a solar house with a solar chimney and a solid adsorption cooling cavity

Abstract This paper presents a parametric analytical study on the enhancement of natural ventilation in a solar house induced by a solar chimney and a solid adsorption cooling cavity. Some details on sizing such a system are also provided. Theoretical analyses are carried out to investigate the ventilation in the solar house with solar chimney alone, cooling cavity alone or with combined solar chimney and solar adsorption cooling cavity, without considering the wind effects. It is found that on a typical day, the solar house comprising of a 2.5xa0m2 solar chimney, is able to create an airflow rate of more than 150xa0kg/h for the studied house. In addition, the ventilation rate at night is also increased by about 20% with the solar adsorption cooling cavity. It is expected that the proposed concept is useful to be incorporated with a stand-alone building or with a cluster of buildings for some favorable climates.