An experimental and numerical campaign was carried out to investigate the performances of tubes in shell heat exchanger applied to cool down the producer gas of a small-scale commercial wood biomass gasifier built by All Power Labs. Producer gas is contaminated with soot and tars that condensate under 300 °C, for this reason the heat exchanger was designed in order to have an in-situ cleaning mechanism. The heat exchanger was tested both with standard plain tubes and with a set of metal twisted tapes (TT) with the aim of enhancing the heat transfer between producer gas and water. Temperatures and mass flows analyses shown a maximum increase of thermal power output and overall heat transfer coefficient respectively of 19% and 76% when TT are applied to the standard plain tubes in shell heat exchanger. Numerical simulations shown a consistency in the trends giving an average discrepancy with experimental results of the 12%.
A novel closed-cycle gas turbine power system is now under development by the GWF Power Systems Company for cogeneration applications. Nominally the system produces 5 megawatts (MW) of electric power and 80,000 lb/hr (36,287 kg/hr) of 1000 psig (6895 kPa) steam. The heat source is an atmospheric fluidized bed combustor (AFBC) capable of using low-cost solid fuels while meeting applicable emission standards. A simple, low-pressure ratio, single spool, turbomachine is utilized. This paper describes the system and related performance, as well as the development and test efforts now being conducted. The initial commercial application of the system will be for Enhanced Oil Recovery (EOR) of the heavy crudes produced in California.
Structural ceramics have been proposed for gas turbines and turbochargers, and there is worldwide interest and activity aimed at developing and evaluating ceramics for these applications. This paper describes a currently active program for evaluation of ceramics for passenger car turbochargers. Results to date are encouraging and indicate that continued evaluation is desirable.
Monatomic gas mixtures have low Prandtl numbers, as low as 0.25 or even lower, compared to about 0.7 for air. In a closed Brayton cycle using a low Prandtl number working gas, the three heat exchangers in the cycle will in general be smaller than in a comparable cycle using air. A system study has been made to compare several promising monatomic gases with air, and to explore the economic incentive to replace air in the closed Brayton cycle with a monatomic gas.
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