Showing papers on "Thermal efficiency published in 1989"

Solid electrolyte fuel cell

Abstract: In a solid electrolyte fuel cell [1,2,3], reactant gases are directed by the reactant gas distributing means [11A,11B] to flow radially between its central [5,6] and peripheral portions [14] and this obviates the need to provide an overall gas seal between the individual components of the fuel cell. A gas seal, if necessary at all, may be provided in selected areas. This permits the individual members of the fuel cell to freely slide with respect to one another during thermal expansion or contraction. The radial flow of reactant gas streams effectively reduces the travel path, and hence the concentration gradient, of the reactant gases. This contributes to the accomplishment of a solid electrolyte fuel cell having improved reliability and characteristics. As a further advantage, the discharged reactant gases may be burnt in a combustion chamber and a solid electrolyte fuel cell having a higher thermal efficiency can be realized by making use of the resulting heat of combustion.

An optimal endoreversible three‐heat‐source refrigerator

Abstract: An endoreversible three‐heat‐source refrigerator only affected by thermal resistance, like a reversible three‐heat‐source refrigerator, may be treated as a combined cycle of a two‐heat‐source engine driving a two‐heat‐source refrigerator. The theory of finite time thermodynamics in two‐heat‐source cycles is then used to analyze it and derive its basic optimum relation. Thus, the fundamental effect of thermal resistance on the optimal performance of a three‐heat‐source refrigerator is expounded. The conclusions obtained here are more realistic than those of classical thermodynamics. They provide some new theoretical bases for further exploitation of the three‐heat‐source refrigeration apparatus that applies to ‘‘cheap’’ heat sources, such as solar energy, geothermal energy, waste heat, and so on.

Thermodynamic cycles with nearly universal maximum-work efficiencies

Abstract: Important thermodynamic heat engine cycles can be regarded as special cases of a more universal 'generalised' cycle. For specific choices of a continuously variable parameter, this generalised cycle reduces to the Carnot, Otto, Joule-Brayton, Diesel and other known cycles. Of particular interest is the thermal efficiency when characteristic temperatures between the highest and lowest operating temperatures (T+ and T-) are chosen to maximise the work output per cycle. This maximum-work efficiency is found to be equal to, or to be well approximated by, the Curzon-Ahlborn efficiency, eta CA identical to 1-(T-/T+)1/2 for a broad spectrum of cycles and temperatures.

Efficiency combined cycle power plant

Abstract: The efficiency of a combined cycle power plant is improved by preheating fuel supplied to a combustion turbine. The flow rate of feed water through an economizer section of a heat recovery steam generator is increased, and the excess flow, over that required to sustain saturated steam production in an evaporator section, is flowed through a heat exchanger to preheat the fuel.

Asymptotic Effectiveness-NTU Formulas for Multipass Plate Heat Exchangers

Abstract: Journal of heat transfer proceedings published by ASME. Please see www.ASME.org for the complete proceedings.

Compact cogeneration system

Abstract: A compact cogeneration system in which a catalytic converter is positioned within otherwise unused space in an exhaust gas heat exchanger employed to heat water. Exhaust gases from an internal combustion engine of a packaged cogeneration system are directed through a single- or two-stage catalytic converter in a central cylindrical housing of the heat exchanger, then are diverted to pass in counterflow over a water-containing coil in an annulus surrounding the housing.

Power transmission apparatus for internal combustion engine including supercharger

Abstract: According to the present invention, a power transmission apparatus for an internal combustion engine (2) having a supercharger (1) attached thereto is constructed such that thermal energy included in exhaust gas discharged from a turbine (T) in the supercharger is recovered by a waste heat recovering turbine (3) thereby to drive the waste heat recovering turbine (3), auxiliary units (9), (10) for a cooling system of the internal combustion engine (2) are driven by power generated by the waste heat recovering turbine (3) which has been driven and the power generated by the wasted heat recovering turbine (3) is then transmitted to a crankshaft (12) of the internal combustion engine (2) via a coupling (6) for interrupting power transmission in an operational region where the internal combustion engine is rotated at a low speed or in an operational region where the internal combustion engine is rotated under a low load.

Flow and heat transfer characteristics of stirling engine regenerator in oscillating flow

Abstract: For the design of stirling engine, the basic data on various regenerator materials are required to be offered which have to be incorporated to the design by computerized simulation. The, pressure loss and gas temperature were instantaneously measured for various regenerator materials installed in oscillating fluid flow. Hydraulic diameter is used as the representative length defined by friction factor and Reynold's number, and flow characteristics of different materials were able to be unifomly adjusted. It was found that heat regeneration loss was able to be evaluated by utilizing the hydraulic diameter, length of regenerator, mean temperature on both side of regenerator, mean heat flow. Such simple eavaluation method is effective when it is applyed to actual engine. By using the frictional loss factors and heat regenerating loss obtained by this study, the effect of wire diameter and length of regenerator on indicated thermal efficiency was clarified. 14 refs., 12 figs., 1 tab.

Thermomagnetic mechanical heat engines

Abstract: Thermomagnetic heat engines that convert thermal energy into mechanical energy are described. These heat engines utilize the thermomagnetic effect which is a property of ferromagnetic materials whereby their magnetization changes with temperature. A computer model is developed from which the performance of the device can be determined. Design curves are included which give the overall dimension, operating parameters, and thermal efficiency of thermomagnetic heat engines operating between a thermal source of 90, 150, or 225 °C and a thermal sink of 25 °C.

Effect of combustion chamber insulation on the performance of a low heat rejection diesel engine with exhaust heat recovery

Abstract: A computer simulation of the turbocharged turbocompound diesel engine system is used to study the effect of combustion chamber insulation on the performance of low heat rejection system configurations with exhaust heat recovery. The analysis is carried out for zirconia coatings of various thickness applied on the cylinder head and piston. It is found that an intercooled turbocompound engine derives a modest thermal efficiency benefit from insulation, e.g. 4.3% improvement at a 60% reduction in heat loss. The addition of Rankine compounding can improve the thermal efficiency of the turbocompound engine by 10–14%, depending on the level of insulation and the system configuration. Furthermore, Rankine compounding can make the otherwise inferior performance of a non-intercooled engine match the performance of an intercooled engine. Finally, use of an insulating material of low conductivity and low heat capacity can increase the thermal efficiency benefits, but at the expense of increased component thermal loading.

Combined gas-turbine and steam-turbine power plant and method for utilization of the thermal energy of the fuel to improve the overall efficiency of the power-plant process

Abstract: The invention concerns a combined gas-turbine and steam-turbine power plant, which comprises heat transfer members which interconnect a pressurized dryer (26) and waste-heat recovery members (22), by means of which the recovered thermal energy of the exhaust gases from the gas turbine (20) can be transferred directly or through the steam turbine into the dryer (26) for the drying of a water-containing material, advantageously fuel, and for the passing of the steam produced as injection steam to the gas turbine (20). The invention also concerns a method for improving the efficiency of a power-plant process.

A New 150-MW High-Efficiency Heavy-Duty Combustion Turbine

Abstract: The 501F 60-Hz combustion turbine has been developed. It continues a long line of large heavy-duty single-shaft combustion turbines by combining the proven efficient and reliable concepts of the W501D5 with the low NO{sub x} technology of the MW701D, together with the experience of the advanced cooled MF111. The new engine is described along with the improved evolutionary changes made from previous engines. Planned design and performance verification programs including model, full-scale component testing, and full-load engine tests are described. Mature output and efficiency in simple cycle mode will be 145 MW and 34 percent, respectively, with expected combined cycle efficiencies in excess of 50 percent.

Water heater or boiler with improved thermal efficiency

Abstract: A water heater/boiler design is shown having a tank with a submergible, pressurized combustion chamber so that all of the heating surfaces of the combustion chamber are submerged under water. The products of combustion are routed from the submerged combustion chamber to a secondary heat exchanger having heat exchange tubes which are also submerged in the tank. A forced draft burner is used to heat the combustion chamber and the burner inlet air is preheated by passing the inlet air over portions of the secondary heat exchanger located on the exterior of the tank.

Methanol as a Fuel for a Lean Turbocharged Spark ignition Engine

Abstract: Lean turbocharged operation with methanol was characterized using a single-cylinder spark, ignition engine. Efficiency, exhaust emissions, and combustion properties were measured over a range of air/fuel ratios at two naturally-aspirated and three turbocharged conditions. When compared to stoichiometric, naturally-aspirated operation, the lean turbocharged conditions improved efficiency while reducing carbon monoxide and oxides of nitrogen emissions. However, unburned fuel and aldehyde emissions increased. If used in conjunction with an oxidizing catalyst and appropriate feedback controls, lean turbocharged operation has the potential of improving efficiency and exhaust emissions performance over a stoichiometric, three-way catalyst system.

Butanol as a Blending Agent with Gasoline for I. C. Engines

Abstract: This paper describes an evaluation of butanol as an alternative fuel for internal combustion engines. The evaluation was made by measuring the performance of a four-cylinder automotive spark-ignition engine when fueled with four different fuels. It was found that there was only about 2.5% reduction in the thermal efficiency of the test engine when 20% of the gasoline was replaced by butanol (the brake-specific-fuel-consumption, BSFC, increased by about 6.5%). Butanol was shown to be superior to both methanol and ethanol in terms of higher thermal efficiency (and correspondingly lower BSFC).

Power optimization of a finite-time solar radiant heat engine

Abstract: SYNOPSIS The power output of a simple, finite-time solar radiant heat engine is studied. The model adopted is a reversible Carnot cycle coupled to a heat source and a heat sink by radiant heat transfer. Both the heat source and the heat sink have Infinite heat capacity rate. A mathematical expression is derived for the power output of the irreversible solar radiant heat engine. The maximum power output is found. The maximum bound provides the basis for designing a real solar heat engine and for a performance comparison with existing solar power plants.

Appliance for heating motor vehicles, mainly buses driven with internal combustion engine

Abstract: The invention relates to an appliance for heating motor vehicles, mainly buses driven with internal combustion engine, provided with heat accumulator in heat transfer connection with the exhaust pipe of the engine, and in given case with the space to be heated. The essential feature of the invention is that the heat accumulator (5) is directly connected with the extended coolant circuit of the engine (M)--and in case of additional heat extracting medium through the installation of heat exchanger (3), furthermore circulating pump (24) operated independently from the engine (M) is built into the extended coolant circuit.

Combined cycles for engine-driven heat pumps

Abstract: The performance of three combined absorption/vapour compression cycles was assessed in a theoretical study with regard to their feasibility to enhance the efficiency and capacity of gas-fired internal combustion engine-driven heat pumps. Coefficients of performance and the capacity have been calculated for typical heating and cooling applications. Operating parameters and the heat duties were also investigated. When all of the exhaust heat is used for heat pumping in addition to the work output, then a performance improvement with regard to both, capacity and coefficient of performance, of up to 31% for cooling and 17% for heating can be accomplished with the desorber-absorber heat exchange (DAHX) cycle, and, respectively, 21 and 11% for the simple absorption cycle (SC). The performance increase for the simple cycle with two solution circuits was found to be consistently less than the SC with one solution circuit, and it is therefore not studied to the same extent as the other two. The total heat duty increases up to 32% for the DAHX cycle and 23% for the SC compared with conventional engine-driven systems. The increase in heat transfer area in smaller than the increase in heat duty due to more favourable heat transfer coefficients. Further, the increase in first cost is considerably less than the increase in heat transfer area due to savings deriving from a 15% smaller compressor and a smaller engine.

Design for the 145-MW Blast Furnace Gas Firing Gas Turbine Combined Cycle Plant

Abstract: A 145 MW blast furnance gas firing gas turbine combined cycle plant was designed and installed in a steel works of Japan as a repowering unit. A 124 MW large scale gas turbine with turbine inlet temperature 1150{sup {degrees}}C (1423 K) was adopted as a core engine for the combined cycle plant. The fuel of this gas turbine is blast furnace gas mixed with coke oven gas which are byproducts in steel works, and the calorific value of the mixed gas to be controlled is about 1000 kcal/Nm{sup 3} (4187 kJ/Nm{sup 3}). A specially designed multi-cannular type combustor was developed to burn such a low BTV fuel. The gas turbine, generator, steam turbine and fuel gas compressor are connected to make a single shaft configuration. As a result of this introducing the gas turbine combined cycle plant, the plant thermal efficiency was achieved above 45% (at NET) and the total electricity generation in the works is increased from 243 MW to 317 MW. This paper describes the design features of this combined cycle plant.

Room heating device for vehicle

Abstract: PURPOSE: To contrive the compactness of structure while improving thermal efficiency by interposing a heating device, which generates thermal energy through a heat exchange between liquid-liquid by using viscous fluid, halfway a heater circuit. CONSTITUTION: This room heating device for a vehicle has a heater circuit 19 in which a heater valve 20, opened when a heater switch is closed, is inter posed, and cooling water is guided to a water pump 12 via a water temperature sensor 21, heating device 22 and a heater radiator 44. The outside air is heated in the heater radiator 44 by actuating a subfan 45 and supplied as hot air into a room. The heating device 22 is constituted so as to generate shearing heat in viscous fluid, interposed between both a rotor and a casing, by relative rota tion between the rotor, integrally formed with a shaft connected to an engine output side through a clutch mechanism 29 turned on when an engine tempera ture is not higher than a preset value, and the casing which serves as a rotary unit. COPYRIGHT: (C)1991,JPO&Japio

Gas turbine propulsion unit with a gas generator

Abstract: In a gas generator of a gas turbine, the turbine is provided with more stages than aerodynamically necessary for reducing the turbine rotational speed. As a result thereof, the stresses of the turbine rotor are reduced, the latter can be made of ceramic material, and the turbine inlet temperature can be increased. In order to permit the compressor to continue to operate at optimum rotational speed, the compressor is coupled with the turbine by way of a transmission providing a speed-up. Owing to this arrangement, the thermal efficiency and therewith the economy of the gas turbine can be considerably increased and the heretofore occurring problems with the use of ceramic material in the turbine are solved in a simple manner.

Solid electrolyte fuel cell module

Abstract: PURPOSE: To make a solid electrolyte fuel cell (SOFC) module small and lightweight and to enhance power generating efficiency by unifying a combustion chamber and an SOFC chamber. CONSTITUTION: A solid electrolyte fuel cell main body comprising a hollow cylindrical reaction air heating pipe 22 installed around a solid electrolyte fuel cell 21 and a combustion air supply pipe 23 installed around the pipe 22, a reaction air supply chamber 16 facing a cell chamber-combustion chamber 17 with a fuel supply pipe 24 through an insulating material, and a fuel supply chamber facing the reaction air supply chamber 16 through a metal partition plate 29 are installed. By the installation of the fuel supply pipe, the SOFC chamber also functions as the combustion chamber 17, and the use of the insulating material is remarkably reduced. At the same time, thermal efficiency and power generating efficiency are increased. COPYRIGHT: (C)1991,JPO&Japio

A theoretical and experimental investigation of an absorption refrigeration system for application with solar energy units

Abstract: Application of the second law of thermodynamics to refrigeration systems is useful in identifying the thermodynamic losses and in finding out where improvements might be made. Theoretical absorption refrigeration cycles are analysed using the first law-based equations of energy balances and the second law-based concept of lost work. A thermodynamic efficiency, defined and formulated from the lost work approach, is used to examine a lithium bromide -water absorption cooling cycle with hot water as the heat source and cooling water as the heat sink. The cycle parameters are varied over applicable operating ranges in order to find their effect on the cycle thermodynamic efficiency. To accomplish this objective and to make a parameteric analysis for the L i Br -water absorption cycle under steady-state conditions, two computer programmes are written. The results indicate the system might be improved by better design. The efficiency variation is compared to variations of coefficient of performance found in the literature. A L i BT -water absorption refrigeration system for low hot water temperature applications has been proposed and detailed design aspects have been considered. Fabrication and testing of a laboratory model of the absorption refrigeration system have been described. As new design methodologies of solar energy applications have been developed recently, a study of solar thermal systems for absorption refrigeration has been presented. This includes the classification, description and modelling of solar systems. Types of design procedures of solar systems for absorption refrigeration are discussed and a computer programme has been implemented which prints out the yearly solar fraction of a solar thermal system with daily storage for supplying heat to an absorption cooling cycle. Numerical performance tests are carried out and the results show that the phibar-f chart design method is a simple and convenient mean of predicting the thermal performance of solar systems.

Process and circuit arrangement for controlling a consumer driven by an internal combustion engine

Abstract: A method for controlling a consumer driven by an internal combustion engine 1 is suggested, especially a compressor 2 of an air-conditioning system of a motor vehicle, in which before the compressor is put into operation, the power output of the internal combustion engine is increased by a fixed amount before the compressor is switched on after a predetermined delay. The method is characterized in that the load occurring on the internal combustion engine as a result of the operation of the consumer is determined before the consumer is put into operation, and in that the power output of the internal combustion engine is increased as a function of the expected load, and the consumer is then put into operation. Preferably, to determine the expected load on the internal combustion engine, the pressure in the high-pressure region of the compressor is measured by means of a sensor 6. Thus, the power of the internal combustion engine is matched as closely as possible to the load occurring as a result of the operation of the consumer. Therefore, there is virtually no decrease in power of the internal combustion engine even immediately when the consumer is switched on, thus ensuring a jerk-free switching-on of the consumer. n

Steam turbines for STAG combined-cycle power systems

Abstract: This paper discusses STAG combined-cycle power plants in which turbine configurations have included single, double and four-flow arrangements utilizing last-stage bucket lengths from 10 to 26 inches. The workings of the STAG cycle are explained and their modern features are highlighted.

Space Power Free-Piston Stirling Engine Scaling Study

Abstract: The design feasibility study is documented of a single cylinder, free piston Stirling engine/linear alternator (FPSE/LA) power module generating 150 kW-electric (kW sub e), and the determination of the module's maximum feasible power level. The power module configuration was specified to be a single cylinder (single piston, single displacer) FPSE/LA, with tuning capacitors if required. The design requirements were as follows: (1) Maximum electrical power output; (2) Power module thermal efficiency equal to or greater than 20 percent at a specific mass of 5 to 8 kg/kW(sub e); (3) Heater wall temperature/cooler wall temperature = 1050 K/525 K; (4) Sodium heat-pipe heat transport system, pumped loop NaK (sodium-potassium eutectic mixture) rejection system; (5) Maximum power module vibration amplitude = 0.0038 cm; and (6) Design life = 7 years (60,000 hr). The results show that a single cylinder FPSE/LA is capable of meeting program goals and has attractive scaling attributes over the power range from 25 to 150 kW(sub e). Scaling beyond the 150 kW(sub e) power level, the power module efficiency falls and the power module specific mass reaches 10 kg/kW(sub e) at a power output of 500 kW(sub e). A discussion of scaling rules for the engine, alternator, and heat transport systems is presented, along with a detailed description of the conceptual design of a 150 kW(sub e) power module that meets the requirements. Included is a discussion of the design of a dynamic balance system. A parametric study of power module performance conducted over the power output range of 25 to 150 kW(sub e) for temperature ratios of 1.7, 2.0, 2.5, and 3.0 is presented and discussed. The results show that as the temperature ratio decreases, the efficiency falls and specific mass increases. At a temperature ratio of 1.7, the 150 kW(sub e) power module cannot satisfy both efficiency and specific mass goals. As the power level increases from 25 to 150 kW(sub e) at a fixed temperature ratio, power module efficiency is seen to increase slightly, but at the expense of increased specific mass. An empirical equation relating power module thermal efficiency as a function of power module specific mass, power output, and temperature ratio is developed. Alternative configurations to the single cylinder, direct coupled linear alternator approach are also evaluated, but are shown to have technical drawbacks that lessen their attractiveness. The dynamic balance assembly mass (moving mass and structure) represents 20 to 30 percent of the total single cylinder power module mass. Joining two modules in a balanced opposed configuration eliminates the need for the balancer, and a hot end junction can be made without significant addition of structural mass. Recommendations are made for evaluation of advanced heat pipe concepts, tests of radial flow heat exchangers, and evaluation of high temperature alternator materials.

Reducing energy costs in vapor-compression refrigeration and air conditioning using liquid recycle. I: Comparison of ammonia and R-12

Abstract: Two common refrigerants, ammonia and R-12, are compared on the basis of energy efficiency, superheat rejection, superheat temperatures, and high-pressure heat exchange area

Floating head type heat exchanger

Abstract: The utility model discloses a floating head heat exchanger which is composed of a casing, a heat exchange tube bundle, a tube plate, a floating head, an outer connecting tube, a flange bolt connecter, an expanding unit, etc. The floating head heat exchanger is characterized in that an expansion joint can be connected between the casing and the heat exchange tube bundle, which can eliminate the difference of thermal expansion. The floating head is directly connected with the outer connecting tube, which can decrease the flow resistance. The expansion joint and flange connecting pieces are all arranged outside the casing. The utility model has the advantages of convenient installation, compactness and high thermal efficiency. The floating head heat exchanger has simple structure, small flow resistance and convenient maintenance. The floating head heat exchanger is suitable for operating conditions whose heat transfer agents have large temperature differences. The floating head heat exchanger is especially suitable for heat exchangers with high temperature and pressure, such as the heat exchangers in petroleum trade, the heat exchangers in chemical engineering, etc.