Some Alternative Technologies for Solar Thermal Power Generation

Solar Energy ◽  
2006 ◽  
Author(s):  
Motoaki Utamura ◽  
Yutaka Tamaura ◽  
Hiroshi Hasuike
Keyword(s):  
Heat Exchanger ◽  
Thermal Power ◽  
Thermal Design ◽  
Optical Systems ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Regenerative Heat ◽  
Turbine Inlet ◽  
The Cross ◽  
Field Efficiency

Two advanced optical systems and a highly efficient thermal cycle suitable for beam-down power tower with thermal storage are presented. (1) To increase field efficiency, the “cross beam” heliostat array concept is proposed. Using continuum optical model, the characteristics of the cross beam concept and its economy were investigated. (2) To protect the central reflector (CR) against wind force, a “multi-ring CR” concept is proposed. The concentration performance of multi-ring CRs is calculated using the ray-tracing method. It shows no worse results than the case with a single hyperboloid mirror. (3) The potential of a closed gas turbine cycle with supercritical carbon dioxide as a working fluid was investigated. An optimal cycle configuration involves a regenerative cycle with pre-cooling and inter-cooling cycles, in which theoretically achievable cycle thermal efficiency is 47% at the turbine inlet temperature of 800 K and turbine inlet pressure of 20 MPa. Detailed thermal design of a critical component, regenerative heat exchanger (RHX) is carried out using a newly developed printed heat exchanger (PCHE). It proved to be a feasible design.

A Solar Gas Turbine Cycle With Super-Critical Carbon Dioxide as a Working Fluid

2006 ◽  
Author(s):  
Motoaki Utamura ◽  
Yutaka Tamaura
Keyword(s):  
Carbon Dioxide ◽  
Heat Exchanger ◽  
Molten Salt ◽  
Gas Turbine ◽  
Thermal Power ◽  
Working Fluid ◽  
Regenerative Heat ◽  
Operation Conditions ◽  
Gas Turbine Cycle ◽  
Cycle Efficiency

Solar thermal power generation system equipped with molten salt thermal storage offers continuous operation at a rated power independent of the variation of insolation. A gas turbine cycle for solar applications is studied which works in a moderate temperature range (600–850K) where molten salt stays as liquid stably. It is found that a closed cycle with super-critical state of carbon dioxide as a working fluid is a promising candidate for solar application. The cycle featured in smaller compressor work would achieve high cycle efficiency if cycle configuration and operation conditions are chosen properly. The temperature effectiveness of a regenerative heat exchanger is shown to govern the efficiency. Under the condition of 98% temperature effectiveness, the regenerative cycle with pre- and inter-cooling provides cycle efficiency of as much as 47%. A novel heat exchanger design to realize such a high temperature effectiveness is also presented.

The Heat Transfer Performance of Porous Gas Turbine Blades

1968 ◽  
Vol 72 (696) ◽  
pp. 1087-1094 ◽  
Author(s):  
F. J. Bayley ◽  
A. B. Turner
Keyword(s):  
Gas Turbine ◽  
Turbine Blades ◽  
Engine Performance ◽  
Operating Conditions ◽  
Maximum Temperature ◽  
Specific Power ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Turbine Inlet ◽  
Compression And Expansion

It is well known that the performance of the practical gas turbine cycle, in which compression and expansion are non-isentropic, is critically dependent upon the maximum temperature of the working fluid. In engines in which shaft-power is produced the thermal efficiency and the specific power output rise steadily as the turbine inlet temperature is increased. In jet engines, in which the gas turbine has so far found its greatest success, similar advantages of high temperature operation accrue, more particularly as aircraft speeds increase to utilise the higher resultant jet velocities. Even in high by-pass ratio engines, designed specifically to reduce jet efflux velocities for application to lower speed aircraft, overall engine performance responds very favourably to increased turbine inlet temperatures, in which, moreover, these more severe operating conditions apply continuously during flight, and not only at maximum power as with more conventional cycles.

scholarly journals Investigation of flow non-uniformities in the cross-flow heat exchanger with elliptical tubes

2019 ◽  
Vol 108 ◽  
pp. 01009 ◽  
Author(s):  
Stanisław Łopata ◽  
Paweł Ocłoń ◽  
Tomasz Stelmach
Keyword(s):  
Heat Exchanger ◽  
Measurement Data ◽  
Cross Flow ◽  
Flow Distribution ◽  
Transitional Flow ◽  
Working Fluid ◽  
Elliptical Cross ◽  
Flow Heat ◽  
The Cross ◽  
Inflow Conditions

In heat exchangers, especially those with the cross-flow arrangement, it is nearly impossible to achieve the uniform distribution of the working fluid in the tubular space with the currently used inlet and outlet chambers (in some constructions as well). The improper inflow conditions to individual tubes, including those with an elliptical cross-section - often used because of their favorable features compared to round tubes, is the cause of improper heat transfer. In this respect, transitional flow is of particular importance. This flow regime is complex and challenging to model. Therefore, it is necessary to perform experimental verification. For this purpose, an appropriate stand was built, allowing to investigate the flow of the working fluid (water) to the elliptical tubes in the cross-current heat exchanger. The paper presents the results of measurements for manifold geometry, which are currently used in practice (for heat exchanger constructions). The analysis of the measurement data confirms the nonuniform flow distribution to individual tubes of the heat exchanger.

Analysis of Energetic, Design and Operational Criteria When Choosing an Adequate Working Fluid for Small ORC Systems

2009 ◽  
Author(s):  
Jorge Faca˜o ◽  
Armando C. Oliveira
Keyword(s):  
Thermal Stability ◽  
Low Temperature ◽  
Heat Source ◽  
Specific Volume ◽  
Saturated Vapor ◽  
Saturation Pressure ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Turbine Inlet ◽  
Cycle Efficiency

Small cogeneration (CHP) systems may lead to a significant reduction of primary energy consumption and harmful emissions. Low temperature Rankine cycles, that can be assisted by solar energy, are a possible solution for producing combined electricity and useful heat. These cycles usually use an organic working fluid. This study presents an analysis of the energetic, design and operational features, that have to be taken into account when choosing an adequate working fluid for these Organic Rankine Cycles (ORC). When using renewable energies as a heat source, like solar or geothermal, the cycles may operate at temperatures between 120°C and 230°C. A system producing 5 kW of electricity was considered as a basis of comparison. Several fluids were analysed: n-dodecane, water, toluene, cyclohexane, n-pentane, HFE7100, R123, isobutane and R245fa. The organic dry fluids, with a positive slope of the saturated vapor curve in a T-s diagram, are in principle desirable for low temperature applications, simplifying turbine design. The degree to which the fluids are drying, is generally related to their molecular weight or molecular complexity. Practical issues, like thermal stability, toxicity, flammability and cost are considered. The thermodynamic cycle efficiency is also important. The saturated vapor specific volume gives an indication of condenser size, which is related to system initial cost. A super-atmospheric (>100 kPa) saturation pressure eliminates infiltration gases, which is important for operational reasons, because infiltration reduces system efficiency. The degree of superheating was optimized for maximum cycle efficiency, with a quadratic approximation method. This optimization makes it possible to decide if it is better to have saturated vapor or superheated vapor at turbine inlet, for a fixed turbine inlet temperature. For a heat source temperature of 120°C, only toluene and isobutane present a small advantage in superheating. It is difficult to find the best fluid, which has simultaneously: high cycle efficiency, low vapor specific volume at turbine outlet, super-atmospheric saturation pressure, good thermal stability, small environmental impact, small toxicity and no flame propagation. From the point of view of cycle efficiency, n-dodecane presents the best performance. However, this fluid presents the highest saturated vapor specific volume (resulting in a larger condenser) and the smallest condenser saturation pressure (resulting in infiltration of gases). The best candidates for the cycle regarding all the aspects are: toluene, cyclohexane and n-pentane. Comparing the three fluids, toluene presents the highest efficiency, the highest impact in environment and the biggest vapor specific volume. N-pentane presents the smallest cycle efficiency and smallest vapor specific volume, but is the unique fluid with super-atmospheric saturation pressure. Cyclohexane is the fluid with lowest impact in environment.

scholarly journals Conceptual Design of a Pulverized Coal Furnace for a Utility Size Closed-Cycle, Gas-Turbine Power Plant

1979 ◽  
Author(s):  
H. J. Strumpf
Keyword(s):  
Heat Exchanger ◽  
Power Plant ◽  
Gas Turbine ◽  
Conceptual Design ◽  
Pulverized Coal ◽  
Temperature Cycle ◽  
Inlet Temperature ◽  
Closed Cycle ◽  
Turbine Inlet Temperature ◽  
Turbine Inlet

A study has recently been completed for the Department of Energy on the conceptual design of coal-fired, closed-cycle, gas-turbine power plants that operate at high turbine-inlet temperatures and use air as the cycle fluid. This paper describes the design of one type of heater system for such a power plant — a pulverized coal furnace. Designs are presented for a 1550 F (843 C) turbine inlet temperature cycle that utilizes metallic superalloy heat exchanger tubes and a 1750 F (954 C) turbine inlet temperature cycle that utilizes ceramic heat exchanger tubes. The heaters consist of two sections — a radiant section where heat is transferred primarily by radiation from the pulverized coal luminous flame, and a convective section where heat is transferred primarily by forced convection from the nonluminous combustion gas. To maintain flame stability in the furnace, a minimum power density criterion must be met. This requires modularization of the radiant heaters.

scholarly journals Experimental Investigation of a Small-Scale ORC Power Plant Using a Positive Displacement Expander with and without a Regenerator

Energies ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1452 ◽  
Author(s):  
Collings ◽  
Mckeown ◽  
Wang ◽  
Yu
Keyword(s):  
Heat Exchanger ◽  
Power Plants ◽  
Large Scale ◽  
Internal Heat ◽  
Expansion Ratio ◽  
Operating Conditions ◽  
Working Fluid ◽  
Small Scale ◽  
Regenerative Heat ◽  
Positive Displacement

While large-scale ORC power plants are a relatively mature technology, their application to small-scale power plants (i.e., below 10 kW) still encounters some technical challenges. Positive displacement expanders are mostly used for such small-scale applications. However, their built-in expansion ratios are often smaller than the expansion ratio required for the maximum utilisation of heat sources, leading to under expansion and consequently higher enthalpy at the outlet of the expander, and ultimately resulting in a lower thermal efficiency. In order to overcome this issue, one possible solution is to introduce an internal heat exchanger (i.e., the so-called regenerator) to recover the enthalpy exiting the expander and use it to pre-heat the liquid working fluid before it enters the evaporator. In this paper, a small-scale experimental rig (with 1-kW rated power) was designed and built that is capable of switching between regenerative and non-regenerative modes, using R245fa as the working fluid. It has been tested under various operating conditions, and the results reveal that the regenerative heat exchanger can recover a considerable amount of heat when under expansion occurs, increasing the cycle efficiency.

scholarly journals Exergy analysis of internal regeneration in supercritical cycles of ORC power plant

2012 ◽  
Vol 33 (3) ◽  
pp. 48-60
Author(s):  
Aleksandra Borsukiewicz-Gozdur
Keyword(s):  
Heat Exchanger ◽  
Power Plant ◽  
Heat Source ◽  
Organic Rankine Cycle ◽  
Rankine Cycle ◽  
Working Fluid ◽  
Heat Sources ◽  
Regenerative Heat ◽  
Hot Air ◽  
Thermal Oil

Abstract In the paper presented is an idea of organic Rankine cycle (ORC) operating with supercritical parameters and so called dry fluids. Discussed is one of the methods of improving the effectiveness of operation of supercritical cycle by application of internal regeneration of heat through the use of additional heat exchanger. The main objective of internal regenerator is to recover heat from the vapour leaving the turbine and its transfer to the liquid phase of working fluid after the circulation pump. In effect of application of the regenerative heat exchanger it is possible to obtain improved effectiveness of operation of the power plant, however, only in the case when the ORC plant is supplied from the so called sealed heat source. In the present paper presented is the discussion of heat sources and on the base of the case study of two heat sources, namely the rate of heat of thermal oil from the boiler and the rate of heat of hot air from the cooler of the clinkier from the cement production line having the same initial temperature of 260 oC, presented is the influence of the heat source on the justification of application of internal regeneration. In the paper presented are the calculations for the supercritical ORC power plant with R365mfc as a working fluid, accomplished has been exergy changes and exergy efficiency analysis with the view to select the most appropriate parameters of operation of the power plant for given parameters of the heat source.

Development of a Maintenance Program for Major Gas Turbine Hot Gas Path Parts

2000 ◽  
Author(s):  
Hideto Moritsuka ◽  
Tomoharu Fujii ◽  
Takeshi Takahashi
Keyword(s):  
Gas Turbine ◽  
Power Plants ◽  
Thermal Power ◽  
Management Program ◽  
Combined Cycle ◽  
Inlet Temperature ◽  
Turbine Inlet Temperature ◽  
Maintenance Schedule ◽  
Hot Gas ◽  
Turbine Inlet

The thermal efficiency of gas turbine combined cycle power generation plants increase significantly in accordance with turbine inlet temperature. Gas turbine combined cycle power plants operating at high turbine inlet temperature are popular as a main thermal power station among our electric power companies in Japan. Thus, gas turbine hot gas parts are working under extreme conditions which will strongly affect their lifetime as well as maintenance costs for repaired and replaced parts. To reduce the latter is of major importance to enhance cost effectiveness of the plant. This report describes a gas turbine maintenance management program of main hot gas parts (combustor chambers, transition peices, turbine 1st. stage nozzles and 1st. stage buckets) for management persons of gas turbine combined cycle power stations in order to obtain an optimal gas turbine maintenance schedule considering rotation, repair and replacement or exchange of those parts.

EXERGY ANALYSIS OF A VAPOR COMPRESSION–VAPOR ABSORPTION CASCADE SYSTEM

2013 ◽  
Vol 21 (04) ◽  
pp. 1350026 ◽  
Author(s):  
GULSHAN SACHDEVA ◽  
VAIBHAV JAIN ◽  
S. S. KACHHWAHA
Keyword(s):  
Heat Exchanger ◽  
Cooling Capacity ◽  
Working Fluid ◽  
Inlet Temperature ◽  
Vapor Compression ◽  
Cascade System ◽  
Structural Bond ◽  
Wide Range ◽  
Vapor Absorption ◽  
Absorption Section

In this paper, second law analysis has been done for the vapor compression–vapor absorption (VC–VA) cascade system. Ammonia–water is considered as the working pair in absorption section and R407C is dealt as the working fluid in VC section. Exergy destruction or the irreversibility rate is determined in each components of VC–VA cascade system, for a wide range of cooling capacity by considering a variable speed reciprocating compressor. Further in this, Coefficient of structural bond (CSB) analysis is carried out to quantify the effect of varying the generator temperature, effectiveness of solution heat exchanger, inlet temperature of external fluids in evaporator/condenser and some other variables. Solution heat exchanger and the condenser are reported to have high CSB value, so have a great scope of improvement to reduce the irreversibility rate of the whole system.

scholarly journals A heat pipe heat recovery heat exchanger for a mini-drier

2006 ◽  
Vol 17 (1) ◽  
pp. 50-57 ◽  
Author(s):  
A Meyer ◽  
R T R T Dobson
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Theoretical Model ◽  
Heat Pipe ◽  
Experimental Testing ◽  
Thermal Design ◽  
Working Fluid ◽  
Transfer Coefficients ◽  
Maximum Heat ◽  
Maximum Heat Transfer

This paper considers the thermal design and the experimental testing of a heat pipe (thermosyphon) heat exchanger for a relatively small commercially available mini-drier. The purpose of the heat exchanger is to recover heat from the moist waste air stream to preheat the fresh incoming air. The working fluid used was R134a and the correlations are given for the evaporator and condenser inside heat transfer coefficients as well as for the maximum heat transfer rate. The theoretical model and computer simulation program used for the thermal design calculations are described. The validity of the as-designed and manufactured heat exchanger coupled to the drier is experimentally verified. The theoretical model accurately predicted the thermal performance and a significant energy savings and a reasonable payback period was achieved.

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