Article

Dynalene/water correlations to be used for condensation of CO2 in brazed plate heat exchangers

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  • Exponent, Inc.
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Abstract

Experimental study of condensation of carbon dioxide in brazed plate heat exchangers is the main objective of this research project. However, it is essential to characterize the single-phase flow through these minichannel heat exchangers in order to analyze and formulate the two-phase flow. In this manuscript, the open literature on the subject is reviewed first, the facility for testing the entire system is then described, and the initial results on the single-phase flow are presented at the end. Three brazed plate heat exchangers with different interior configurations, each consisting of three channels, are considered and tested in this study. For the two-phase analysis, carbon dioxide is the working fluid, flowing through the middle channel, while dynalene is the cooling fluid, flowing through the side channels. For the single-phase analysis, data was taken using hot and cold water flow through the middle and side channels, respectively. Data was also taken using hot water in the middle and chilled dynalene in the surrounding channels. The modified Wilson plot technique was applied to obtain single-phase heat transfer coefficients, and Fanning friction factor was estimated for the pressure drop. The resulted correlations were within reasonable range of standard deviation and uncertainty, and compared well with other relevant studies.

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... A number of studies [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] that investigated the single-phase heat transfer and pressure drop in BPHEs and some GPHEs, from 1981 to 2017, are included in Table A1 in Appendix A. A total of 28 heat transfer correlations for GPHEs were summarized by Ayub [26], in which most correlations adopted the form of the Dittus Boelter equation [27] for the convective heat transfer coefficient in tubes. For single-phase flow, studies have shown that the geometric parameters such as the chevron angle b ð Þ, hydraulic D h ð Þ or equivalent diameter D e ð Þ, corrugation pitch (k) and enlargement factor / ð Þ, have a strong influence on the thermal and hydraulic performance of the heat exchanger. ...
... Furthermore, most single-phase correlations are reported for water-to-water configurations for which it was often found that the Nusselt number correlation for the hot and cold side was the same. Hayes and Jokar [8] conducted experiments with hot water and chilled dynalene and demonstrated that it is essential to report correlations for the hot side and cold side when using two different fluids. ...
... Water-to-water experiments were first conducted before the water-to-refrigerant experiments. This allowed evaluation of the water-side heat transfer coefficient (h w ), see Eq. (8), and therefore subsequent evaluation of the heat transfer coefficient on the refrigerant side (h r ). The modified Wilson Plot technique [36] was used to evaluate h w and the unknown constants C 1 , C 2 and C 3 in Eq. (8). ...
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... where ρ m is the quality-weighted average density, kg/m 3 . and the single-phase friction factor was calculated using the following equation [24]: ...
... Therefore, p c, in, UB value was reduced to p c, in k − 1 to force the iteration algorithm to choose a lower saturation pressure. For a positive residual, the adjustment was instead made to p c, in, LB : Assembly of the CO 2 GSHP Tube connection port diameter (mm) 27 27 Surface enhancement chevron ** chevron ** * The plate thickness and channel spacing were taken from [24] as representative values ** The details of the chevron enhancement are not known. ...
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... Details of major components pertaining to pressure readings as well as discussions for each loop are provided in this section; however, more detailed information, especially related to heat transfer, can be found in previously published works of the authors [12,13]. ...
... Fig. 7 shows the resulted correlations along with the experimental data points for each test, where the average standard deviations were less than 4%. A thorough analysis and comparison of the single-phase flow in these heat exchangers was presented in a previously published work by the authors [13]. It is important to note that the comparisons between studies do not necessarily show that one heat exchanger is better than another, because the heat exchanger correlations in different studies use different sized heat exchangers with similar (not always exact) inclination angles. ...
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... Specifications of the PHXs for the condenser/gas-cooler and the LLSL-HX. The plate thickness and channel spacing are taken from[44] as representative values. ...
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... The experim coefficients established f correlations [4]. The above e β is in degre 10% and 8% Figure 4 tely 30 two-p n, there are t and film con to condense 1 below. ...
... The test data were reduced to heat transfer coefficients under specified steadystate conditions. Brine-side heat transfer coefficients were established first, and for validation purposes, they were compared to existing single-phase correlations for plate exchangers in the open literature, as presented in detail by Hayes and Jokar [4]. Next, a thorough two-phase study with uncertainty analysis was conducted on the condensation of carbon dioxide in the three brazed plate heat exchangers (BPHE). ...
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... A thorough single-phase analysis was completed which entailed a study of hot and cold water as well as hot water exchanging heat with dynalene. A full literature review as well as single-phase schematics, experimental setup, instrumentation, test procedures, results and discussion were all previously published by the authors of this study, Hayes and Jokar [17]. A review of the single-phase heat transfer correlations in all three brazed plate heat exchanger plates is given in Table 4. ...
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