Improving the Efficiency of Stirling Engines for Use in Solar Distributed Electricity, Heating, and Cooling

2013 ◽  
Author(s):  
Travis M. Schubert ◽  
Shirin Jouzdani ◽  
Kevin P. Hallinan
Keyword(s):  
Heat Exchanger ◽  
Thermal Efficiency ◽  
Effective Means ◽  
Heat Engine ◽  
Stirling Engine ◽  
Future Application ◽  
Film Material ◽  
Expansion Chamber ◽  
Thermal Switch ◽  
Low Mass

Limiting solar power is the inability to cost effectively store energy. The most cost effective means to store solar energy is thermally in the ground, which can then be used for direct conversion to electricity. However, doing so is limited by a historically poor thermal efficiency of such engines. A novel Stirling engine is posed which more closely mimics a Carnot heat engine. It does this through the use of a new passive thermal ‘switch’ which permits heat flow into the expansion chamber of the Stirling engine only when the temperature of the chamber is above a desired value. Ideally heat would be added only at the end of the compression stroke and the beginning of the expansion stroke. Central to this thermal switch is the use of a vanadium dioxide (VO2) low mass heat exchanger internal to the expansion chamber. This low mass heat exchanger allows the film material to track and react to the temperature changes within the expansion chamber, permitting it to transfer heat only when needed. An adiabatic model of this enhanced solar Stirling engine is developed. Results indicate that the thermal efficiency can be nearly doubled, delivering a second law efficiency of over 0.6. Further, a year round overall efficiency accounting for losses in the Stirling engine and solar thermal collectors of 7% appears to be feasible when this engine is integrated with ground solar storage, providing the necessary power to meet loads in a low energy residence. Such results demonstrate promise for future application of this technology.

Valved Heat Engine Working on Modified Atkinson Cycle

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
C. V. Ramesh
Keyword(s):  
Thermal Efficiency ◽  
Heat Engine ◽  
Engine Performance ◽  
Inertial Force ◽  
Expansion Ratio ◽  
Stirling Engine ◽  
Performance Criteria ◽  
Stirling Cycle ◽  
Heat Engines ◽  
Atkinson Cycle

There is immense scope for the development of heat engines that can directly convert solar and biochemical renewable sources of thermal energy to high-grade energy. Regenerative Stirling cycle heat engine with its performance criteria of highest thermal efficiency and high mean effective pressure is theoretically the best engine for small capacity reciprocating heat engine. However, the practical Stirling engine performance is far from the ideal. As an alternative, practical heat engines based on thermodynamic cycles (without regeneration) other than the Stirling cycle have been suggested. This paper deals with a new concept in the design of reciprocating heat engine working on modified Atkinson cycle. In the Atkinson cycle, expansion ratio being higher than compression ratio, the thermal efficiency is better than that of the standard Otto cycle. Heat engine design based on the suggested modified Atkinson cycle can be an alternative to the practical Stirling engine. In the conceptual mechanical design of the engine suggested here, apart from utilizing the principle of Atkinson cycle for achieving higher thermal efficiency, the mechanical configuration of the reciprocating engine ensures a high degree of inertial force balancing. This can result in reduced vibrations in the mountings of the power units.

Carbohydrate and Protein Supplements, an Effective Means for Maintaining Exercise-Induced Glucose Metabolism Homeostasis

2021 ◽  
Vol 11 (6) ◽  
pp. 1120-1128
Author(s):  
Dingguo Ruan ◽  
Hong Deng ◽  
Xiaoyang Xu
Keyword(s):  
Blood Glucose ◽  
Glucose Metabolism ◽  
Normal Saline ◽  
Glucose Transporter ◽  
Glycogen Synthesis ◽  
Effective Means ◽  
Recovery Period ◽  
Future Application ◽  
Glut 4 ◽  
Exercise Induced

This study aimed to verify the effects of an independently developed carbohydrate and protein (CHO+P) beverage (7.2% oligosaccharide and 1.6% soy-polypeptide) supplement on exerciseinduced glucose metabolism and associated gene expression. Mice received 1 mL/100 g body weight of normal saline (group C; n = 36) or CHO+P (group E; n = 36) at 30 min before an immediately after exercise. Mice without exercise and supplementation served as normal controls (group NC; n = 9). The expression levels related to glucose metabolism were measured at 0, 4, 12, and 24 h after exercise (n = 9 per group). The blood glucose, insulin, and liver glycogen contents in groups C and E were dramatically lower than group NC immediately after exercise. Those in group E were significantly higher than group C, with few differences between the two. Muscle glycogen was restored more quickly when the CHO+P beverage was consumed compared to normal saline. Furthermore, exercise-induced increase in glucose transporter-4 (GLUT-4) mRNA could be depressed by CHO+P supplementation but enhanced in GLUT-4 protein. Interleukin-6 (IL-6) showed a double peak curve in the recovery period, but IL-6 increased again in group E earlier than group C. These findings confirmed that the beverage has significantly improved time in maintaining blood glucose stability, reducing glycogen consumption, accelerating glycogen resynthesis, and repairing injury in rats. This study suggests the future application of this beverage in humans with experimental support and provides a scientific direction for promoting glycogen synthesis and recovery through nutrition.

Cost–Effective Retrofit Of A Palm Oil Refinery Using Pinch Analysis

2012 ◽  
Author(s):  
Sharifah Rafidah Wan Alwi ◽  
Muhammad Azan Tamar Jaya ◽  
Zainuddin Abdul Manan
Keyword(s):  
Heat Exchanger ◽  
Palm Oil ◽  
Thermal Efficiency ◽  
Capital Investment ◽  
Heat Recovery ◽  
Cost Effective ◽  
Oil Refinery ◽  
Pinch Analysis ◽  
Heat Exchanger Network ◽  
Maximum Heat

Kilang penapisan minyak sawit lazimnya melibatkan proses penggunaan tenaga yang tinggi. Peningkatan kecekapan tenaga adalah amat penting bagi memastikan keuntungan tercapai. Kertas kerja ini menggunakan teknik analisis jepit bagi memaksimumkan penggunaan semula haba dan meningkatkan kecekapan sistem rangkaian haba sedia ada di kilang penghasilan minyak sawit, tertakluk kepada kekangan–kekangan proses. Langkah–langkah yang terlibat ialah penetapan sasaran guna semula haba maksimum diikuti dengan reka bentuk rangkaian haba yang ekonomik. Aplikasi teknik berkenaan kepada kilang penghasilan minyak sawit telah menghasilkan pengurangan penggunaan haba panas dan sejuk sebanyak 700 kW (21%), atau penjimatan kos utiliti sebanyak RM370,787, dengan pelaburan kapital sebanyak RM656,293 dan jangka pulangan balik selama 1.77 tahun. Kata kunci: Analisis jepit; minyak kelapa sawit; sedia ada; rangkaian pemindahan haba; kitar semula haba maksimum A palm oil refinery involves energy–intensive processes. Maximizing thermal efficiency of palm oil refinery is crucial for the plant profitability. This work implements a pinch analysis retrofit technique to maximize heat recovery and thermal efficiency of a palm oil refinery, subject to the existing process constraints. The procedures involve setting the maximum heat recovery targets and cost–effective retrofit of the heat exchanger network (HEN). Application of the technique on a palm oil refinery results in reduction of 700 kW (21%) heating and cooling loads or a saving of RM370,787, incurring a capital investment of about RM656,293 and a payback period of 1.77 years. Key words: Pinch analysis; palm oil; retrofit; heat exchanger network; maximum heat recovery

Sadi Carnot

2020 ◽  
pp. 329-367
Author(s):  
Robert T. Hanlon
Keyword(s):  
Thermal Efficiency ◽  
Heat Engine ◽  
Conserved Quantity ◽  
Closed Cycle ◽  
Maximum Work ◽  
Caloric Theory

Carnot sought to better understand the performance of the Cornish engine for the benefit of France. His ground-breaking analysis involved new theories on thermal efficiency, maximum work, and closed-cycle operation. Carnot proposed an ideal heat engine that achieved the best possible efficiency, regardless (surprisingly) of the nature of the working substance. Unfortunately, embedded deep inside Carnot’s powerful analysis was a single major flawed assumption: the caloric theory of heat in which heat is treated as a conserved quantity.

Characterization of a dynamic micro heat engine with integrated thermal switch

2006 ◽  
Vol 16 (9) ◽  
pp. S262-S269 ◽  
Author(s):  
L W Weiss ◽  
J H Cho ◽  
K E McNeil ◽  
C D Richards ◽  
D F Bahr ◽  
...  
Keyword(s):  
Heat Engine ◽  
Thermal Switch ◽  
Micro Heat Engine

Advanced Gas Turbine and High Performance Gas-Steam Combined Cycle Plant With Blade Cooling Air Controlling

2006 ◽  
Author(s):  
Tadashi Tsuji
Keyword(s):  
Power Generation ◽  
Heat Exchanger ◽  
Gas Turbine ◽  
Thermal Efficiency ◽  
Gas Turbines ◽  
Combined Cycle ◽  
Hot Water ◽  
Blade Cooling ◽  
Combined Cycle Plant ◽  
Cooling Air

Air cooling blades are usually applied to gas turbines as a basic specification. This blade cooling air is almost 20% of compressor suction air and it means that a great deal of compression load is not converted effectively to turbine power generation. This paper proposes the CCM (Cascade Cooling Module) system of turbine blade air line and the consequent improvement of power generation, which is achieved by the reduction of cooling air consumption with effective use of recovered heat. With this technology, current gas turbines (TIT: turbine inlet temperature: 1350°C) can be up-rated to have a relative high efficiency increase. The increase ratio has a potential to be equivalent to that of 1500°C Class GT/CC against 1350°C Class. The CCM system is designed to enable the reduction of blade cooling air consumption by the low air temperature of 15°C instead of the usual 200–400°C. It causes the turbine operating air to increase at the constant suction air condition, which results in the enhancement of power and thermal efficiency. The CCM is installed in the cooling air line and is composed of three stage coolers: steam generator/fuel preheater stage, heat exchanger stage for hot water supplying and cooler stage with chilled water. The coolant (chilled water) for downstream cooler is produced by an absorption refrigerator operated by the hot water of the upstream heat exchanger. The proposed CCM system requires the modification of cooling air flow network in the gas turbine but produces the direct effect on performance enhancement. When the CCM system is applied to a 700MW Class CC (Combined Cycle) plant (GT TIT: 135°C Class), it is expected that there will be a 40–80MW increase in power and +2–5% relative increase in thermal efficiency.

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