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Modeling and experimental analysis of the solar radiation in a CO2 direct-expansion solar-assisted heat pump
KTH, School of Industrial Engineering and Management (ITM), Energy Technology.ORCID iD: 0000-0002-9902-2087
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2019 (English)In: Applied Thermal Engineering, ISSN 1359-4311, E-ISSN 1873-5606, p. 160-172Article in journal (Refereed) Published
Abstract [en]

In the present work is presented the dynamic model of an evaporator of a Direct Expansion Solar Assisted Heat Pump (DX-SAHP), charged with CO2. This dynamic model was used to analyze the evaporator response to sudden variations in the solar radiation. Two strategies are used to make the system reach the steady state after the heat pump start-up. The first one is the usual balances of mass, energy and momentum. The second strategy consisted in impose an equal refrigerant mass flow rate at the evaporator inlet and outlet. Both strategies were able to conduct the system to a steady state, however, the second one required less computational effort. The mathematical model was validated using experimental data and employed to perform several simulations. The results obtained with the mathematical model revealed that a small variation of the solar radiation leads to a significant variation in the superheat, therefore requiring an immediate action of the expansion device. It was concluded that an Electronic Expansion Valve (EEV) would be better suited to meet the needs of rapid interventions on the mass flow rate at the evaporator inlet, and also because the DX-SAHP could operate in a continuous transient condition in some seasons.

Place, publisher, year, edition, pages
Elsevier Ltd , 2019. p. 160-172
Keywords [en]
Direct expansion, Expansion device, Experimental analysis, Modeling, Solar-assisted heat pump, Carbon dioxide, Dynamic models, Evaporators, Heat pump systems, Mass transfer, Models, Pumps, Solar radiation, Computational effort, Electronic expansion valves, Expansion devices, Small variations, Solar assisted heat pump, Transient conditions, Expansion
National Category
Mechanical Engineering
Identifiers
URN: urn:nbn:se:kth:diva-248201DOI: 10.1016/j.applthermaleng.2018.11.045ISI: 000460845100017Scopus ID: 2-s2.0-85056692273OAI: oai:DiVA.org:kth-248201DiVA, id: diva2:1304530
Note

QC 20190412

Available from: 2019-04-12 Created: 2019-04-12 Last updated: 2019-04-12Bibliographically approved

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Palm, Björn

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