scholarly journals CFD ANALYSIS OF TEMPERATURE FIELD IN PELLET STOVE AS A GENERATOR OF AN ABSORPTION HEAT PUMP

2020 ◽  
pp. 163
Author(s):  
Marko Ilic ◽  
Velimir Stefanović ◽  
Saša Pavlović ◽  
Gradimir Ilić
Keyword(s):  
Temperature Field ◽  
Heat Pump ◽  
Waste Heat ◽  
Heat Pumps ◽  
Temperature Fields ◽  
Working Fluid ◽  
Comprehensive Overview ◽  
Absorption Heat Pump ◽  
Design And Optimization ◽  
The Balkans

The paper presents an initial CFD study on adopting the biomass-pellet usage in a generator of an absorption heat pump by obtaining the temperature field inside the biomass furnace. Contemporary absorption technologies are mostly based on the use of gas and other waste heat as a driving force in the Generator, where the two-component working fluid splits into the refrigerant and the absorbent. There are few or no absorption heat pumps that work directly on biomass - pellets. In the Balkans, biomass - pellets are a frequent and renewable source of thermal energy. The aim of this paper is to initially research the possibility of an absorption generator to work directly on available pellets. Following this idea, a comprehensive overview of contemporary absorption technology is given with a physical and mathematical model of the small pellet stove in FLUENT, which will be modified to adapt the generator. In the beginning, temperature fields are obtained by simulation inside the furnace and on its surfaces. Work showed that the temperature field has enough potential for triggering the absorption process as temperatures in the upper part of the stove are above 400°C at the heating capacity of around 13 kW up to 20 kW. The implemented work and the obtained results could serve as a useful reference for further design and optimization of the generator of AHP for direct Biomass utilization for a middle size system.

Heat Integration of Absorption Heat Pump in a Milk Powder Dairy

2000 ◽  
Author(s):  
Jens Møller Andersen
Keyword(s):  
Heat Pump ◽  
Waste Heat ◽  
Cooling System ◽  
Milk Powder ◽  
Electricity Consumption ◽  
Heat Pumps ◽  
Heat Integration ◽  
Absorption Heat Pump ◽  
Absorption Cooling ◽  
Absorption Cooling System

Abstract Heat integration with absorption heat pumps requires investigation of many types of plant designs. In this article, it is concluded that in many cases high temperature absorption systems for heat recovery are more economically feasible than absorption systems for cooling purposes. The conclusion is based on a project where the scope was to investigate technical and economical possibilities for heat integration of an absorption heat pump in a milk powder plant. The first idea behind the project was to use the waste heat from the rejected air to drive an absorption cooling system to reduce the electricity consumption for cooling proposes. The model of the plant was based on simulations as a background for a time averaged COP model. It was concluded that an absorption system for generating low temperature steam is more feasible.

Absorption Heat Pump/Refrigeration System Utilizing Ionic Liquid and Hydrofluorocarbon Refrigerants

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Sarah Kim ◽  
Yoon Jo Kim ◽  
Yogendra K. Joshi ◽  
Andrei G. Fedorov ◽  
Paul A. Kohl
Keyword(s):  
Ionic Liquid ◽  
Heat Pump ◽  
Waste Heat ◽  
Working Fluid ◽  
Coolant Temperature ◽  
Low Grade ◽  
Outlet Temperature ◽  
Refrigeration System ◽  
Pump System ◽  
Absorption Heat Pump

The ionic liquid butylmethylimidazolium hexafluorophosphate (bmim)(PF6) and five different hydrofluorocarbon refrigerants were investigated as the working fluid pairs for a waste-heat driven absorption heat pump system for possible applications in electronics thermal management. A significant amount of the energy consumed in large electronic systems is used for cooling, resulting in low grade waste heat, which can be used to drive an absorption refrigeration system if a suitable working fluids can be identified. The Redlich–Kwong-type equation of state was used to model the thermodynamic conditions and the binary mixture properties at the corresponding states. The effects of desorber and absorber temperatures, waste-heat quality, and system design on the heat pump performance were investigated. Supporting experiments using R134a/(bmim)(PF6) as the working fluid pair were performed. Desorber and absorber outlet temperatures were varied by adjusting the desorber supply power and the coolant temperature at the evaporator inlet, respectively. For an evaporator temperature of 41 °C, which is relevant to electronics cooling applications, the maximum cooling-to-total-energy input was 0.35 with the evaporator cooling capability of 36 W and the desorber outlet temperature in the range of 50 to 110 °C.

scholarly journals Economic Analysis of Heat Pump Recovery System for Circulating Water Waste Heat in Power Plant

2021 ◽  
Vol 256 ◽  
pp. 02011
Author(s):  
Ze Wang ◽  
Honghong Shen ◽  
Qunyin Gu ◽  
Daoyuan Wen ◽  
Gang Liu ◽  
...  
Keyword(s):  
Power Plant ◽  
Energy Saving ◽  
Heat Pump ◽  
Waste Heat ◽  
Heat Pumps ◽  
Water Saving ◽  
Absorption Heat Pump ◽  
Circulating Water ◽  
Cold Source ◽  
Heat Pump Unit

The use of heat pump technology to recover the waste heat of circulating water from the power plant instead of steam extraction for heating can not only improve the thermal efficiency of the unit and reduce the loss of cold source, but also has great advantages in energy saving. This paper uses absorption and compression heat pumps to recover the waste heat of circulating water in the power plant to study its energy-saving benefits. Under the same heating load, the economics of the two heat pumps are calculated and analyzed. The results show that the energy-saving benefits of absorption heat pump units are far greater than compression units. But in terms of water saving, the water saving capacity of the compression heat pump unit is higher than that of the absorption heat pump.

scholarly journals Local Heating Networks with Waste Heat Utilization: Low or Medium Temperature Supply?

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 954 ◽  
Author(s):  
Hanne Kauko ◽  
Daniel Rohde ◽  
Armin Hafner
Keyword(s):  
Low Temperature ◽  
Heat Pump ◽  
Urban Areas ◽  
Waste Heat ◽  
Local Heating ◽  
District Heating ◽  
Heat Pumps ◽  
Hot Water ◽  
Local Network ◽  
Medium Temperature

District heating enables an economical use of energy sources that would otherwise be wasted to cover the heating demands of buildings in urban areas. For efficient utilization of local waste heat and renewable heat sources, low distribution temperatures are of crucial importance. This study evaluates a local heating network being planned for a new building area in Trondheim, Norway, with waste heat available from a nearby ice skating rink. Two alternative supply temperature levels have been evaluated with dynamic simulations: low temperature (40 °C), with direct utilization of waste heat and decentralized domestic hot water (DHW) production using heat pumps; and medium temperature (70 °C), applying a centralized heat pump to lift the temperature of the waste heat. The local network will be connected to the primary district heating network to cover the remaining heat demand. The simulation results show that with a medium temperature supply, the peak power demand is up to three times higher than with a low temperature supply. This results from the fact that the centralized heat pump lifts the temperature for the entire network, including space and DHW heating demands. With a low temperature supply, heat pumps are applied only for DHW production, which enables a low and even electricity demand. On the other hand, with a low temperature supply, the district heating demand is high in the wintertime, in particular if the waste heat temperature is low. The choice of a suitable supply temperature level for a local heating network is hence strongly dependent on the temperature of the available waste heat, but also on the costs and emissions related to the production of district heating and electricity in the different seasons.

scholarly journals Critical Analysis of Process Integration Options for Joule-Cycle and Conventional Heat Pumps

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 635 ◽  
Author(s):  
Limei Gai ◽  
Petar Sabev Varbanov ◽  
Timothy Gordon Walmsley ◽  
Jiří Jaromír Klemeš
Keyword(s):  
Heat Pump ◽  
Process Integration ◽  
Waste Heat ◽  
Correct Choice ◽  
Heat Pumps ◽  
Coefficient Of Performance ◽  
Large Temperature ◽  
Temperature Changes ◽  
Application Range ◽  
Source And Sink

To date, research on heat pumps (HP) has mainly focused on vapour compression heat pumps (VCHP), transcritical heat pumps (TCHP), absorption heat pumps, and their heat integration with processes. Few studies have considered the Joule cycle heat pump (JCHP), which raises several questions. What are the characteristics and specifics of these different heat pumps? How are they different when they integrate with the processes? For different processes, which heat pump is more appropriate? To address these questions, the performance and integration of different types of heat pumps with various processes have been studied through Pinch Methodology. The results show that different heat pumps have their own optimal application range. The new JCHP is suitable for processes in which the temperature changes of source and sink are both massive. The VCHP is more suitable for the source and sink temperatures, which are near-constant. The TCHP is more suitable for sources with small temperature changes and sinks with large temperature changes. This study develops an approach that provides guidance for the selection of heat pumps by applying Process Integration to various combinations of heat pump types and processes. It is shown that the correct choice of heat pump type for each application is of utmost importance, as the Coefficient of Performance can be improved by up to an order of magnitude. By recovering and upgrading process waste heat, heat pumps can save 15–78% of the hot utility depending on the specific process.

scholarly journals Possibility of Calcium Oxide from Natural Limestone Including Impurities for Chemical Heat Pump

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 803
Author(s):  
LanXin Lai ◽  
Toshio Imai ◽  
Motohiro Umezu ◽  
Mamoru Ishii ◽  
Hironao Ogura
Keyword(s):  
Heat Pump ◽  
Calcium Oxide ◽  
Waste Heat ◽  
Heat Pumps ◽  
Raw Material ◽  
Hydration Reaction ◽  
Chemical Heat ◽  
Chemical Heat Pump ◽  
Thermogravimetric Analyzer ◽  
Save Energy

Improving energy recycle is an important way to save energy resources and preserve the global environment. Chemical heat pump (CHP) is a technology for saving energy, which utilizes chemical reactions to store thermal energy such as waste heat and solar heat, then release it to provide heat for heating/cooling/refrigeration. For a practical CHP, it is necessary to find cheaper and more stable supply materials. In order to evaluate the possibility of calcium oxide from natural Ofunato natural limestone including impurities, we compare Ofunato limestone with Kawara natural limestone and Garou natural limestone from Japan. These calcium oxides worked as a reactant for CaO/H2O/Ca(OH)2 CHP by repeated hydration/dehydration reaction cycle experiments in a thermogravimetric analyzer. As a result, Ofunato CaO exhibits a high hydration reaction rate after decarbonization at 1223 K for 5 h. The reactivity increased by the repeated hydration reaction although the first hydration rate was low. Furthermore, the sintering of impurities in Ofunato limestone occur easier than that in Kawara limestone with lower impurities. The impurities adhered to the surface of the CaO particle to make specific surface area of CaO particle smaller, which could inhibit hydration reaction of CaO particle. Even if Ofunato limestone contains some impurities, it can be utilized as a raw material for chemical heat pumps.

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

2020 ◽  
Vol 10 (1) ◽  
pp. 323 ◽  
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.

Design and Optimization of Waste Heat Recovery Unit Using Carbon Dioxide as Cooling Fluid

2014 ◽  
Author(s):  
Geir Skaugen ◽  
Harald T. Walnum ◽  
Brede A. L. Hagen ◽  
Daniel P. Clos ◽  
Marit J. Mazzetti ◽  
...  
Keyword(s):  
Heat Exchanger ◽  
Heat Recovery ◽  
Waste Heat Recovery ◽  
Waste Heat ◽  
Working Fluid ◽  
Design And Optimization ◽  
Power Cycle ◽  
Turbine Efficiency ◽  
Recovery Unit ◽  
Process Simulations

This paper describes design and optimization of a Waste Heat Recovery Unit (WHRU) for a power cycle which uses CO2 as a working fluid. This system is designed for offshore installation to increase gas turbine efficiency by recovering waste heat from the exhaust for production of additional power. Due to severe constraints on weight and space in an offshore setting, it is essential to reduce size and weight of the equipment to a minimum. Process simulations are performed to optimize the geometry of the WHRU using different objective functions and thermal-hydraulic models. The underlying heat exchanger model used in the simulations is an in-house model that includes the calculation of weight and volume for frame and structure for the casing in addition to the thermal-hydraulic performance of the heat exchanger core. The results show that the for a set of given process constraints, optimization with respect to minimum total weight or minimum core weight shown similar results for the total installed weight, although the design of heat exchanger differs. The applied method also shows how the WHRU geometry can be optimized for different material combinations.

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