S. Seetharamu

Absorption-resorption heating cycles with the new working pairs R21-NMP and R21-DMA

The new working pairs, R21-NMP and R21-DMA, find potential application as working pairs for the single stage Resorption Heat Pump (RHP) and the Resorption Heat Transformer (RHT) cycles. A thermodynamic cycle analysis with these pairs shows that single stage RHPs have high COPs in their entire range of operation. RHTs show higher temperature boosts (up to 47 K) than the simple absorption heat transformers. Absorber temperatures of up to 400 K can be achieved in a single stage RHT system using R21 as the refrigerant. However, absorption-resorption systems have inherent limitations on the range of operating temperatures. Besides, they necessitate a higher pump work as compared to simple single stage absorption heating systems.

Optimal heat extraction from an updraft biomass reactor

Abstract This paper presents the design of gas-water and gas-air heat exchangers for extraction of thermal energy from updraft biomass gasifiers in the firing rate range 10–120 kg/h. Mathematical models are developed to study the sensitivity of the heat exchanger efficiency and effectiveness to geometric and flow variables. Optimal parameters to suit the biomass reactor have been evolved. The calculated heat transfer coefficients have been compared with experimental results obtained in test gas-water and gas-air heat exchangers with an observed deviation between −25 and + 17%. In conclusion, system efficiencies of about 75–80% can be achieved by choice of appropriate operating flow regimes and heat exchanger sizes.

Comparative study of biomass fuels in an updraft gasifier

The authors discuss an updraft biomass gasification reactor with a maximum firing rate of 25 kg/h. The novel design features of this reactor are a self-generated steam injection system at the appropriate points, a natural-draft air-control system, and the choice of an appropriate reactor chamber volume. The reactor is useful for producing process heat. The heat is extracted by means of a heat-exchange unit, which is placed directly above the reactor at a maximum efficiency of 49%. The system produces hot water or steam continuously. Another feature is that a variety of biomass fuels, such as wood wastes, sawdust, coconut fiber, and briquettes of cattle manure and dried leaves, can be fired in this reactor.<<ETX>>

Efficient, low cost blades for wind mills

The design and fabrication of and field experience with wind mill blades of a simple curved vane type are described. The skeleton of the blade is of a spar and rib structure and is made from mild steel pipe, rods, and T-sections. The required twist is given to the frame, and the blade surface is obtained by closely weaving the furniture-grade polythene canes. Various design factors affecting the final blade construction and improvements for increasing the life of the blade are discussed. The results of weathering tests on the blade material under accelerated laboratory conditions and actual field conditions are discussed. The cost levels of different blade materials are given for comparison.<<ETX>>