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34 pages, 7169 KiB

Open AccessArticle

Investigation of a Hybridized Cascade Trigeneration Cycle Combined with a District Heating and Air Conditioning System Using Vapour Absorption Refrigeration Cooling: Energy and Exergy Assessments

by Larry Orobome Agberegha, Peter Alenoghena Aigba, Solomon Chuka Nwigbo, Francis Onoroh, Olusegun David Samuel, Tanko Bako, Oguzhan Der, Ali Ercetin and Ramazan Sener

Energies 2024, 17(6), 1295; https://doi.org/10.3390/en17061295 - 7 Mar 2024

Cited by 12 | Viewed by 1873

Abstract

The insufficiency of energy supply and availability remains a significant global energy challenge. This work proposes a novel approach to addressing global energy challenges by testing the supercritical property and conversion of low-temperature thermal heat into useful energy. It introduces a combined-cascade steam-to-steam trigeneration cycle integrated with vapour absorption refrigeration (VAR) and district heating systems. Energetic and exergetic techniques were applied to assess irreversibility and exergetic destruction. At a gas turbine power of 26.1 MW, energy and exergy efficiencies of 76.68% and 37.71% were achieved, respectively, while producing 17.98 MW of electricity from the steam-to-steam driven cascaded topping and bottoming plants. The cascaded plant attained an energetic efficiency of 38.45% and an exergy efficiency of 56.19%. The overall cycle efficiencies were 85.05% (energy) and 77.99% (exergy). More than 50% of the plant’s lost energy came from the combustion chamber of the gas turbine. The trigeneration system incorporated a binary NH₃–H₂O VAR system, emphasizing its significance in low-temperature energy systems. The VAR system achieved a cycle exergetic efficiency of 92.25% at a cooling capacity of 2.07 MW, utilizing recovered waste heat at 88 °C for district hot water. The recovered heat minimizes overall exergy destruction, enhancing thermal plant performance. Full article

(This article belongs to the Section J: Thermal Management)

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18 pages, 3119 KiB

Open AccessArticle

A Waste Heat-Driven Cooling System Based on Combined Organic Rankine and Vapour Compression Refrigeration Cycles

by Youcai Liang, Zhibin Yu and Wenguang Li

Appl. Sci. 2019, 9(20), 4242; https://doi.org/10.3390/app9204242 - 11 Oct 2019

Cited by 20 | Viewed by 6336

Abstract

In this paper, a heat driven cooling system that essentially integrated an organic Rankine cycle power plant with a vapour compression cycle refrigerator was investigated, aiming to provide an alternative to absorption refrigeration systems. The organic Rankine cycle (ORC) subsystem recovered energy from the exhaust gases of internal combustion engines to produce mechanical power. Through a transmission unit, the produced mechanical power was directly used to drive the compressor of the vapour compression cycle system to produce a refrigeration effect. Unlike the bulky vapour absorption cooling system, both the ORC power plant and vapour compression refrigerator could be scaled down to a few kilowatts, opening the possibility for developing a small-scale waste heat-driven cooling system that can be widely applied for waste heat recovery from large internal combustion engines of refrigerated ships, lorries, and trains. In this paper, a model was firstly established to simulate the proposed concept, on the basis of which it was optimized to identify the optimum operation condition. The results showed that the proposed concept is very promising for the development of heat-driven cooling systems for recovering waste heat from internal combustion engines’ exhaust gas. Full article

(This article belongs to the Section Energy Science and Technology)

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14 pages, 1095 KiB

Open AccessArticle

A LiBr-H₂O Absorption Refrigerator Incorporating a Thermally Activated Solution Pumping Mechanism

by Ian W. Eames

Entropy 2017, 19(3), 90; https://doi.org/10.3390/e19030090 - 26 Feb 2017

Cited by 6 | Viewed by 8305

Abstract

This paper provides an illustrated description of a proposed LiBr-H₂O vapour absorption refrigerator which uses a thermally activated solution pumping mechanism that combines controlled variations in generator vapour pressure with changes it produces in static-head pressure difference to circulate the absorbent solution between the generator and absorber vessels. The proposed system is different and potentially more efficient than a bubble pump system previously proposed and avoids the need for an electrically powered circulation pump found in most conventional LiBr absorption refrigerators. The paper goes on to provide a sample set of calculations that show that the coefficient of performance values of the proposed cycle are similar to those found for conventional cycles. The theoretical results compare favourably with some preliminary experimental results, which are also presented for the first time in this paper. The paper ends by proposing an outline design for an innovative steam valve, which is a key component needed to control the solution pumping mechanism. Full article

(This article belongs to the Special Issue Advances in Applied Thermodynamics II)

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15 pages, 501 KiB

Open AccessFeature PaperArticle

Computational Model of a Biomass Driven Absorption Refrigeration System

by Munyeowaji Mbikan and Tarik Al-Shemmeri

Energies 2017, 10(2), 234; https://doi.org/10.3390/en10020234 - 16 Feb 2017

Cited by 10 | Viewed by 5561

Abstract

The impact of vapour compression refrigeration is the main push for scientists to find an alternative sustainable technology. Vapour absorption is an ideal technology which makes use of waste heat or renewable heat, such as biomass, to drive absorption chillers from medium to large applications. In this paper, the aim was to investigate the feasibility of a biomass driven aqua-ammonia absorption system. An estimation of the solid biomass fuel quantity required to provide heat for the operation of a vapour absorption refrigeration cycle (VARC) is presented; the quantity of biomass required depends on the fuel density and the efficiency of the combustion and heat transfer systems. A single-stage aqua-ammonia refrigeration system analysis routine was developed to evaluate the system performance and ascertain the rate of energy transfer required to operate the system, and hence, the biomass quantity needed. In conclusion, this study demonstrated the results of the performance of a computational model of an aqua-ammonia system under a range of parameters. The model showed good agreement with published experimental data. Full article

(This article belongs to the Special Issue Biomass for Energy Country Specific Show Case Studies)

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11 pages, 1927 KiB

Open AccessTechnical Note

Determination of Concentration of the Aqueous Lithium–Bromide Solution in a Vapour Absorption Refrigeration System by Measurement of Electrical Conductivity and Temperature

by Salem M. Osta-Omar and Christopher Micallef

Data 2017, 2(1), 6; https://doi.org/10.3390/data2010006 - 19 Jan 2017

Cited by 11 | Viewed by 13929

Abstract

Lithium–bromide/water (LiBr/water) pairs are widely used as working medium in vapour absorption refrigeration systems where the maximum expected temperature and LiBr mass concentration in solution are usually 95 ℃ and 65%, respectively. Unfortunately, published data on the electrical conductivity of aqueous lithium–bromide solution are few and contradictory. The objective of this paper is to develop an empirical equation for the determination of the concentration of the aqueous lithium–bromide solution during the operation of the vapour absorption refrigeration system when the electrical conductivity and temperature of solution are known. The present study experimentally investigated the electrical conductivity of aqueous lithium–bromide solution at temperatures in the range from 25 ℃ to 95 ℃ and concentrations in the range from 45% to 65% by mass using a submersion toroidal conductivity sensor connected to a conductivity meter. The results of the tests have shown this method to be an accurate and efficient way to determine the concentration of aqueous lithium–bromide solution in the vapour absorption refrigeration system. Full article

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22 pages, 3637 KiB

Open AccessArticle

Design and Thermodynamic Analysis of a Steam Ejector Refrigeration/Heat Pump System for Naval Surface Ship Applications

by Cüneyt Ezgi and Ibrahim Girgin

Entropy 2015, 17(12), 8152-8173; https://doi.org/10.3390/e17127869 - 11 Dec 2015

Cited by 11 | Viewed by 14705

Abstract

Naval surface ships should use thermally driven heating and cooling technologies to continue the Navy’s leadership role in protecting the marine environment. Steam ejector refrigeration (SER) or steam ejector heat pump (SEHP) systems are thermally driven heating and cooling technologies and seem to be a promising technology to reduce emissions for heating and cooling on board naval surface ships. In this study, design and thermodynamic analysis of a seawater cooled SER and SEHP as an HVAC system for a naval surface ship application are presented and compared with those of a current typical naval ship system case, an H₂O-LiBr absorption heat pump and a vapour-compression heat pump. The off-design study estimated the coefficient of performances (COPs) were 0.29–0.11 for the cooling mode and 1.29–1.11 for the heating mode, depending on the pressure of the exhaust gas boiler at off-design conditions. In the system operating at the exhaust gas boiler pressure of 0.2 MPa, the optimum area ratio obtained was 23.30. Full article

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