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A low capacity twin‐bed adsorption refrigeration system has been built with R134a as a refrigerant and activated carbon as the adsorbent. Simple tube‐in‐tube heat exchangers have been fabricated and have been used as the adsorber beds. Activated carbon (granular type) has been filled in the annular space of the inner tube and outer tube. A plate heat exchanger has been used as the condenser and the temperature of cooling water has been maintained between 25°C and 30°C, also the evaporator has been custom designed as per requirements. A mathematical model has also been developed and the results obtained have been found to be comparable. While operating the system in the single‐bed mode a cooling power of 250.4 W has been obtained with a coefficient of performance (COP) of 0.38 with an average evaporator temperature of 18.4°C against a predicted value of 263.7 W with a COP of 0.41. While operating in the twin‐bed mode a cooling power of 281.3 W with a COP of 0.47 with an average evaporator temperature of 17.6°C has been obtained against a predicted value of 294.5 W with a COP of 0.52. [ABSTRACT FROM AUTHOR]

Adsorption Refrigeration Systems (ARS) are gaining considerable importance in view of their applications in several areas and in particular to transport industries. The refrigerants used in these systems are also quite acceptable from the points of view of Global warming and Ozone depletion. In our efforts to develop such refrigeration systems for transport vehicles, a sub-atmospheric Silicagel-Water ARS (SWARS) and a positive pressure Activated Carbon / R134a ARS (ACRARS) have been designed, fabricated and experimentally studied to evaluate their performances. A lumped parameter simulation model has been used to describe the dynamic behavior of these systems. The rate of adsorption / desorption of the refrigerants in both cases are assumed to be governed by the Linear Drive Force (LDF) model. The amount of refrigerants in adsorbent at equilibrium conditions are assumed to be described by the equations for modified Freundlich and Dubinin-Astakhov models for SWARS and ACRARS respectively. The simulation models are numerically solved by finite difference method with the simulation programs coded in MATLAB. The simulation results are found to be in good agreement with experimental results in both cases. A two-bed Silicagel-water adsorption refrigeration system has been built and it is well known that the refrigeration is produced at the evaporator. If the refrigeration power is not used to cool an external heat load (for example, by allowing the circulation of water through the heat exchanger coil embedded in the evaporator), the evaporator reaches the lowest temperature. This is the no-load condition at which the refrigeration power produced by the system is zero. When the evaporator temperature is higher than this lowest temperature, a finite refrigeration power is produced which increases with increasing evaporator temperature. The above Silicagel-water system reaches the lowest temperature of 5.3°C at no load conditions and produces a refrigeration power of ~ 284 ± 9 W at 18°C, which refers to the average temperature (Tavg) of the flowing water through the heat exchanger coil within the evaporator. An experimental COP of 0.52 has been measured for this system. On the other hand, the simulation model predicts a refrigeration power of 325 W at 18 °C with a COP of 0.55. Using Activated Carbon - R134a pair, a four bed adsorption refrigeration system has been designed and developed. The refrigeration system is designed such that it can be operated in three different configurations and they are: (A) A single bed (i.e. all four beds arranged in parallel), (B) A twin bed, (i.e. the four beds get grouped in two pairs and undergo the opposite processes of the adsorption cycle and (C) Four independent beds each undergoing the different processes of the adsorption cycle. The measured lowest temperatures under no-load conditions are 14.5 °C, 13.3 °C and 11.9 °C for configurations A, B and C respectively as against the predictions of the simulations which are 13.3°C, 12.5 °C & 11.4°C. The experimentally measured refrigeration powers are 430 ± 13 W, 556 ± 17 W and 657 ± 20 W at the Tavg temperature of 28.5 °C for configurations A, B and C respectively. On the other hand, the refrigeration powers predicted by simulation are 450 W, 582 W and 690 W for the respective configurations. The measured COP values are 0.5, 0.65 and 0.70 for configurations A, B and C respectively as against those predicted by simulation which are 0.54, 0.67 and 0.73 respectively. It is observed that the experimental results are reasonably in good agreement with those predicted by the simulations. The highlight of the present work is that the Activated Carbon - R134a Adsorption Refrigeration System produces continuous refrigeration power which can be very useful for practical applications. Efforts are now underway to adopt this refrigeration system for cooling of truck cabins. [ABSTRACT FROM AUTHOR]

A generalized linear two-point hedging rule is proposed for the operation of a water supply reservoir that integrates four possible linear two-point hedging types, which are identified based on two possibilities of starting water availability and two possibilities of ending water availability, arising from the respective bounds on release and carryover storage being active. The proposed rule is appropriately parameterized for implementation into a simulation-optimization (S-O) framework to investigate the trade-off between the shortage characteristics, total shortage ratio, and Vulnerability resulting from the long-term monthly operation of a water supply reservoir, and the efficacy of the same is illustrated using a case example, namely the Dharoi reservoir, located on the Sabarmati River in India. Significant improvement in the reservoir performance trade-off is achieved by the proposed generalized linear two-point hedging rule over the conventional standard operating policy (SOP)-based linear two-point hedging rule for the cases of constant as well as time-varying hedging parameters. [ABSTRACT FROM AUTHOR]

In this communication, we report the development of a cryosorption pump, whose pumping speeds are higher at least by a factor of 1.5 compared to the commercial pumps in specific pressure ranges. This uses a material of high adsorbing capacity along with an adhesive of high thermal conductivity. The measured pumping speeds of these pumps for different gases such as nitrogen, argon, hydrogen, and helium are higher than the commercial cryopumps in the pressure range from 5 x 10-6 mbar to 5 x 10-5 mbar. The developed pump will be quite useful for fusion applications. [ABSTRACT FROM AUTHOR]