Compact Diesel Engine Waste-Heat Driven Ammonia-Water Absorption Heat Pump Modeling and Performance Maximization Strategies

Abstract An investigation of the best ways to achieve optimal performance from a waste-heat-driven ammonia-water absorption heat pump over a wide range of operating conditions is presented. Waste-heat is recovered using an exhaust gas heat exchanger and delivered to the desorber by a heat transfer fluid loop. The absorber and condenser are hydronically coupled in parallel to an ambient heat exchanger for heat rejection. The evaporator provides chilled water for space-conditioning with a baseline cooling capacity of 2 kW. A detailed thermodynamics model is developed to simulate performance and develop strategies to achieve the best performance in both cooling and heating modes over a range of operating conditions. These parametric studies show that improved coefficients of performance can be achieved by adjusting the coupling fluid temperatures in the evaporator and the condenser/absorber as the ambient temperature varies. With the varying return temperatures, the system is able to provide the 2 kW design cooling capacity for a wide range of ambient temperatures.

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Heat exchanger design optimization for mitigation of diesel engine exhaust fouling

Journal of Energy Resources Technology ◽

10.1115/1.4049416 ◽

2020 ◽

pp. 1-36

Author(s):

Victor C. Aiello ◽

Girish Kini ◽

Marcel Staedter ◽

Srinivas Garimella

Keyword(s):

Design Optimization ◽

Heat Pump ◽

Waste Heat ◽

Large Data ◽

Cooling Capacity ◽

Operating Conditions ◽

Component Level ◽

Pressure Drops ◽

Single Tube ◽

Wide Range

Abstract The design optimization of a diesel exhaust coupled heat and mass exchanger that drives a 2.71 kW cooling capacity absorption heat pump is presented in this study. Fouling layer thermal resistance and pressure drops from single-tube experiments are used to develop a thermodynamic, heat transfer, and pressure drop model for the exhaust coupled desorber. A parametric study is performed to select a desorber design that meets system performance while minimizing footprint. Experimental heat duties and pressure drops are within 10% and 3%, respectively, of the model predictions. Thus, large data sets from single-tube experiments with representative geometries are successful in accounting for fouling effects at the component level. Desorber design optimization based on this approach ensures continued heat pump performance after fouling. This study, along with the single tube experiments, presents a systematic approach to design exhaust-coupled heat exchangers while considering the effects of fouling. These results are applicable for a wide range of waste-heat recovery applications and this method can be extended to different geometries and operating conditions.

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Thermodynamic and Exergoeconomic Analysis of a Supercritical CO2 Cycle Integrated with a LiBr-H2O Absorption Heat Pump for Combined Heat and Power Generation

Applied Sciences ◽

10.3390/app10010323 ◽

2020 ◽

Vol 10 (1) ◽

pp. 323 ◽

Cited By ~ 1

Author(s):

Yi Yang ◽

Zihua Wang ◽

Qingya Ma ◽

Yongquan Lai ◽

Jiangfeng Wang ◽

...

Keyword(s):

Heat Pump ◽

Supercritical Co2 ◽

Waste Heat ◽

Unit Cost ◽

Heating System ◽

Combined Heat And Power ◽

Economic Benefits ◽

Ammonia Water ◽

Absorption Heat Pump ◽

Comparison Results

In this paper, a novel combined heat and power (CHP) system is proposed in which the waste heat from a supercritical CO2 recompression Brayton cycle (sCO2) is recovered by a LiBr-H2O absorption heat pump (AHP). Thermodynamic and exergoeconomic models are established on the basis of the mass, energy, and cost balance equations. The proposed sCO2/LiBr-H2O AHP system is examined and compared with a stand-alone sCO2 system, a sCO2/DH system (sCO2/direct heating system), and a sCO2/ammonia-water AHP system from the viewpoints of energy, exergy, and exergoeconomics. Parametric studies are performed to reveal the influences of decision variables on the performances of these systems, and the particle swarm optimization (PSO) algorithm is utilized to optimize the system performances. Results show that the sCO2/LiBr-H2O AHP system can obtain an improvement of 13.39% in exergy efficiency and a reduction of 8.66% in total product unit cost compared with the stand-alone sCO2 system. In addition, the sCO2/LiBr-H2O AHP system performs better than sCO2/DH system and sCO2/ammonia-water AHP system do, indicating that the LiBr-H2O AHP is a preferable bottoming cycle for heat production. The detailed parametric analysis, optimization, and comparison results may provide some references in the design and operation of sCO2/AHP system to save energy consumption and provide considerable economic benefits.

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