Heat transfer and fluid flow in spray evaporators with application to reducing refrigerant inventory

dc.contributor.advisor Michael B. Pate
dc.contributor.author Moeykens, Shane
dc.contributor.department Mechanical Engineering
dc.date 2018-08-23T14:48:59.000
dc.date.accessioned 2020-06-30T07:05:19Z
dc.date.available 2020-06-30T07:05:19Z
dc.date.copyright Sat Jan 01 00:00:00 UTC 1994
dc.date.issued 1994
dc.description.abstract <p>As the phase-out of chlorofluorocarbons (CFC's) approaches, there is a current need for the development of new vapor compression chillers which can operate with non-CFC refrigerants while still maintaining high operating efficiencies. Redesign of the traditional flooded evaporator used in refrigeration chillers so as to incorporate a spray evaporation capability offers both a potential for increased heat transfer performance and a reduction in refrigerant inventory for a given chiller capacity relative to that found with existing industrial units;This study is an evaluation of the spray evaporation heat transfer performance of refrigerants HFC-134a, HCFC-22, and HCFC-123 with commercially available copper alloy tubes. In addition, the effects of small concentrations of oil on the spray evaporation heat transfer process are also investigated;Two different spray evaporation heat transfer facilities were designed and constructed, namely, a multi-tube facility and a large scale bundle facility. Testing of HFC-134a was conducted on the multi-tube test facility with six different enhanced and low-finned surface copper tubes. These initial tests indicated that enhanced condensation surfaces were better suited for the spray evaporation environment than enhanced boiling surfaces. The pure refrigerant work was followed by lubricant effects testing with two different viscosity polyol-ester oils. It was found that oil concentrations through 5.0% of a 340 SUS polyol-ester oil yielded heat transfer performances greater than those measured in the pure refrigerant testing;Following the initial tests on the multi-tube test facility, large scale bundle work was conducted with all three refrigerants. The performance of HFC-134a was approximately 100 percent greater than that found with HCFC-123, and it was verified that pure HCFC-22 performed better than HFC-134a with two different tube surfaces. Small concentrations of a polyol-ester oil (through 2.5%) increased the spray evaporation heat transfer performance of HFC-134a with all surfaces evaluated. Refrigerant HCFC-22 received less benefit from small concentrations of an alkyl-benzene oil than that seen in the HFC-134a testing with the polyol-ester oil. In a similar film-feed supply rate range as that used in the high-pressure refrigerant testing, small concentrations of a napthenic mineral oil decreased the spray evaporation heat transfer performance of HCFC-123;Limited pool-boiling testing was conducted with pure HFC-134a for comparison with spray evaporation heat transfer results. It was verified that the spray evaporation heat transfer performance of a low-finned tube bundle was better than that found in flooded evaporator testing with the same bundle. More importantly, it was found that the spray evaporation heat transfer performance of an enhanced condensation surface bundle surpassed the pool boiling performance of an enhanced convective boiling surface bundle.</p>
dc.format.mimetype application/pdf
dc.identifier archive/lib.dr.iastate.edu/rtd/10498/
dc.identifier.articleid 11497
dc.identifier.contextkey 6405230
dc.identifier.doi https://doi.org/10.31274/rtd-180813-9748
dc.identifier.s3bucket isulib-bepress-aws-west
dc.identifier.submissionpath rtd/10498
dc.identifier.uri https://dr.lib.iastate.edu/handle/20.500.12876/63650
dc.language.iso en
dc.source.bitstream archive/lib.dr.iastate.edu/rtd/10498/r_9503583.pdf|||Fri Jan 14 18:21:54 UTC 2022
dc.subject.disciplines Mechanical Engineering
dc.subject.keywords Mechanical engineering
dc.title Heat transfer and fluid flow in spray evaporators with application to reducing refrigerant inventory
dc.type article
dc.type.genre dissertation
dspace.entity.type Publication
relation.isOrgUnitOfPublication 6d38ab0f-8cc2-4ad3-90b1-67a60c5a6f59
thesis.degree.level dissertation
thesis.degree.name Doctor of Philosophy
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