Analysis of Cryogenic assisted Ammonia-water power Cycle

Jagannath, K and Sharma , S S and Kini, Achutha U and Prabhu, P R and Manjesh, B (2014) Analysis of Cryogenic assisted Ammonia-water power Cycle. In: 2nd International Conference on Current Trends in Engineering and Management (ICCTEM-2014), 17-19, Mysore.

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Abstract

The demand for energy and electrical power is ever increasing. Efficient and low-cost methods of power generation is a primary requirement for a sustainable use of the available natural resources. The use of non-azeotropic binary mixtures as the working fluid in power cycles has received considerable attention. The motivation for using non-azeotropic binary mixtures is the fact that heat can be supplied or rejected at variable temperature but constant pressure, which can reduce the mismatch between the hot and cold streams and the cycle working fluid. Ammonia-water cycle is one among most prominent methods of power generation with high efficiency and low cost since the mixture of working fluids enable efficient energy recovery. The properties of ammonia and water are suitable for a power cycle working fluid mixture. The substances are soluble in each other and easily separable. Ammonia and water have different boiling temperatures; thus, the ammonia-water mixture evaporates over a large temperature range, which is an advantage for power generation from a sensible heat source. Both substances are inexpensive and extensively used in industry. Ammonia and water have approximately the same molecular weights; hence, a steam turbine can be used in the ammonia-water cycle with only minor alterations. There is also better thermal matching between the heat source and the working fluid. Use of the cryogenic exergy of Liquefied natural gas (LNG) for power generation includes methods which use the LNG as the working fluid in natural gas direct expansion cycles, or its coldness as the heat sink in closed-loop Rankine cycles.Natural gas is considered to be the most environmental friendly fossil fuel and LNG is regarded as a relatively clean energy resource which has very high potential of cold energy that can be efficiently recovered in a power producing process.Because ammonia is a working fluid with a low boiling point and the cold energy generated during the LNG vaporization is used to condense the ammonia turbine exhaust, the ammonia vapor can expand to a much lower temperature compared to a conventional steam Rankine cycle. This paper presents a thermal performance analysis of a combined power cycle which consisted of an ammonia-water cycle with and without regenerator and LNG cycle to utilize low-temperature waste heat in the form of sensible energy. Based on the thermodynamic models of ammonia-water power generation cycles, the effects of the key parameters such as ammonia concentration, turbine inlet pressure and condenser outlet temperature on the system performance are investigated. The results show that the ammonia concentration, turbine inlet pressure and condenser outlet temperature affect greatly the thermodynamic performance of the combined cycle. It is also found that there exists an optimum ammonia concentration to achieve maximum system performance.

Item Type: Conference or Workshop Item (Paper)
Uncontrolled Keywords: Ammonia concentration, Liquefied Natural gas, Regeneration, Heat exchanger
Subjects: Engineering > MIT Manipal > Mechanical and Manufacturing
Depositing User: MIT Library
Date Deposited: 25 Jul 2014 07:13
Last Modified: 25 Jul 2014 07:13
URI: http://eprints.manipal.edu/id/eprint/140236

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