A general correlation to predict the flow boiling heat transfer of R410A in macro-/mini-channels

Improvements in using geothermal sources can be attained through the installation of power plants taking advantage of low and medium enthalpy available in poorly exploited geothermal sites. Geothermal fluids at medium and low temperature could be considered to feed binary cycle power plants using organic fluids for electricity “production” or in cogeneration configuration. The improvement in the use of geothermal aquifers at low-medium enthalpy in small deep sites favours the reduction of drilling well costs, and in addition, it allows the exploitation of local resources in the energy districts. The heat exchanger evaporator enables the thermal heat exchange between the working fluid (which is commonly an organic fluid for an Organic Rankine Cycle) and the geothermal fluid (supplied by the aquifer). Thus, it has to be realised taking into account the thermodynamic proprieties and chemical composition of the geothermal field. The geothermal fluid is typically very aggressive, and it leads to the corrosion of steel traditionally used in the heat exchangers. This paper analyses the possibility of using plastic material in the constructions of the evaporator installed in an Organic Rankine Cycle plant in order to overcome the problems of corrosion and the increase of heat exchanger thermal resistance due to the fouling effect. A comparison among heat exchangers made of commonly used materials, such as carbon, steel, and titanium, with alternative polymeric materials has been carried out. This analysis has been built in a mathematical approach using the correlation referred to in the literature about heat transfer in single-phase and two-phase fluids in a tube and/or in the shell side. The outcomes provide the heat transfer area for the shell and tube heat exchanger with a fixed thermal power size. The results have demonstrated that the plastic evaporator shows an increase of 47.0% of the heat transfer area but an economic installation cost saving of 48.0% over the titanium evaporator.

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“…where the Nusselt number is calculated according to Equation ( 4) in laminar condition [83] and to Equation ( 5) for turbulent regime [84].…”

Section: Shell-side Model Equationsmentioning

confidence: 99%

Modelling of Polymeric Shell and Tube Heat Exchangers for Low-Medium Temperature Geothermal Applications

et al. 2020

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“…That means the convective boiling mechanism was active on the heat transfer mechanism of R-410A in mini-channel. In order to validate the experimental heat transfer coefficient of R410A in both mini-and macro-scale channel, Chien et al [11] compared the data with various heat transfer coefficient correlations [26,[30][31][32][33][34] include both of the correlations developed for mini-scale channel and the ones developed for macro-scale channel. The data bank consists of 452 data points including 61 data with D h > 3.0 mm (macro-scale) and 391 data with D h ≤ 3.0 mm (mini-scale).…”

Section: Figure 7(a) and (B)mentioning

confidence: 99%

“…In order to bring out an overview to the reader, this chapter investigates the experimental results with the wide range of operating conditions as well as the tube diameters, which have been evaluated in our lab in the past [9][10][11] and recently. The influence of mass flux, heat flux and channel diameter on the heat transfer coefficient and pressure drop was well reported.…”

Section: Introductionmentioning

confidence: 99%

Pressure Drop and Boiling Heat Transfer Characteristics of R410A in Macro-Scale and Mini-Scale Channels

Oh¹,

Chien²,

Choi³

et al. 2017

Heat Exchangers - Advanced Features and Applications

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This chapter demonstrates the two-phase flow pressure drop and heat transfer of R410A during boiling in various tube types. The pressure drop and local heat transfer coefficients were obtained for heat fluxes ranging from 10 to 40 kW/m 2 , mass fluxes ranging from 100 to 600 kg/m 2 s, the vapour quality up to 1.0 and the saturation temperatures of 5-15°C. The test sections were made of various tube diameters of 1.5, 3.0, 6.61 and 7.49 mm, respectively. The effect of mass flux, heat flux, saturation temperature and inner tube diameter on pressure drop and heat transfer coefficient was analysed. The experimental results were compared against several existing pressure drop and heat transfer coefficient correlation. New correlations of pressure drop and boiling heat transfer coefficient were also developed in this present study.

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Saturated flow boiling heat transfer: review and assessment of prediction methods

et al. 2018

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A general correlation to predict the flow boiling heat transfer of R410A in macro-/mini-channels

Cited by 11 publications

References 20 publications

Modelling of Polymeric Shell and Tube Heat Exchangers for Low-Medium Temperature Geothermal Applications

Modelling of Polymeric Shell and Tube Heat Exchangers for Low-Medium Temperature Geothermal Applications

Pressure Drop and Boiling Heat Transfer Characteristics of R410A in Macro-Scale and Mini-Scale Channels

Saturated flow boiling heat transfer: review and assessment of prediction methods

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