...) are replacements for R123 and R245fa. All of these replacement refrigerants had measured boiling heat fluxes that were larger than that for R123 for most heat fluxes. For example, for heat fluxes between 10 kWm −2 and 80 kWm −2 , R514A, R1224 yd(Z), and R1336mzz(E) exhibited average heat fluxes that were 30%, 57...

... 10 shows the heat flux ratio averaged between a q ″ PL of 10 kW/m 2 and 40 kW/m 2 as a function of N np / A s for three different boiling surfaces of varied nanoparticle volume fraction and refrigerant/nanolubricant mass fraction. As previously stated, the N np / A s...

... measurements and a refrigerant\lubricant mixture pool-boiling model were used to suggest that increases in thermal conductivity and lubricant viscosity are mainly responsible for the heat transfer enhancement due to nanoparticles. Particle size measurements were used to suggest that particle agglomeration...

...Cristiano Bigonha Tibiriçá; Gherhardt Ribatski; John Richard Thome Experimental flow boiling heat transfer results are presented for horizontal 1.0 and 2.2 mm I.D. (internal diameter) stainless steel tubes for tests with R1234ze(E), a new refrigerant developed as a substitute for R134a with a much...

...Tailian Chen Pool boiling heat transfer has been extensively studied over decades, but the effect of boundary heating conditions on boiling received little attention. In this work, heat transfer coefficients during pool boiling of five different refrigerants (R123, R245fa, R236fa, R134a, and R22...

... in the condensation heat transfer. The experiments were performed using refrigerant R-134a flowing in the annular channel that was cooled on the outside by a counter-current flow of water. The electric fields are established by applying high voltage to a concentric rod electrode inside a grounded tube. The effect...

...Ling-Xiao Zhao; Liang Yang; Chun-Lu Zhang A new neural network modeling approach to the evaporator performance under dry and wet conditions has been developed. Not only the total cooling capacity but also the sensible heat ratio and pressure drops on both air and refrigerant sides are modeled...

...) and high Pr (80–140) numbers that are typically found in secondary refrigeration loop conditions. The effect of horizontal U-bend is also presented. It is shown that the positive effect of thermal development (high Nu number) lasts long because of the technically significant length of the thermally...

...Akhil Agarwal; Srinivas Garimella Condensation pressure drops and heat transfer coefficients for refrigerant R134a flowing through rectangular microchannels with hydraulic diameters ranging from 100 μ m to 200 μ m are measured in small quality increments. The channels are fabricated on a copper...

..., and implications on the through-silicon-via scaling and electrical interconnect congestion are discussed. Also, the thermal and hydraulic performance of several two-phase refrigerants is discussed in comparison with single-phase cooling. The results show that the large internal pressure and the pumping pressure...

...Claudi Martín-Callizo; Björn Palm; Wahib Owhaib; Rashid Ali The present work reports on flow boiling visualization of refrigerant R-134a in a vertical circular channel with an internal diameter of 1.33 mm and 235 mm in heated length. A quartz tube with a homogeneous Indium Tin Oxide coating is used...

... subcooling change. Bubble lift-off radius distribution at higher pressures 29 01 2009 16 07 2009 15 10 2009 boiling bubbles contact angle heat transfer nucleation organic compounds refrigerants A mechanistic model has been proposed in Part I of this paper ( 1...

... mechanism in the refrigerant channel. Various distance frames in the refrigerant channel were also employed to study the influence of the refrigerant mass flux on two-phase flow heat transfer. The tests were conducted at heat fluxes ranging between 4.5 kW / m 2 and 17 kW / m 2 with 134a as refrigerant. Pool...

... and evaporation heat transfer rates. condensation evaporation heat exchangers heat pipes natural convection refrigerants heat pipe thermosyphon heat exchanger R-134a The heat transfer in thermosyphons is based on a continuous cycle of the vaporization and condensation processes...

... of a nanolubricant with half the concentration of CuO nanoparticles (0.5% by volume) resulted in either no improvement or boiling heat transfer degradations with respect to the R134a/polyolester mixtures without nanoparticles. Consequently, significant refrigerant/lubricant boiling heat transfer enhancements...

...Wai Keat Kuan; Satish G. Kandlikar The present work is aimed toward understanding the effect of flow boiling stability on critical heat flux (CHF) with Refrigerant 123 (R-123) and water in microchannel passages. Experimental data and theoretical model to predict the CHF are the focus of this work...

...M. M. Awad 20 03 2007 15 06 2007 25 01 2008 condensation heat transfer microfluidics refrigerants two-phase flow In the paper “Pressure Drop During Refrigerant Condensation Inside Horizontal Smooth, Helical Microfin, and Herringbone Microfin Tubes” (Olivier, J...

...Yirong Jiang; Biswajit Mitra; Srinivas Garimella; Ulf C. Andresen This paper presents the results of an experimental study on condensation heat transfer of refrigerant blends R404A and R410A flowing through horizontal tubes of 9.4 and 6.2 mm inner diameter at nominal pressures of 80% and 90...

... of refrigerants R-22, R-134a, and R-407C inside a series of typical horizontal smooth, micro-fin, and herringbone tubes at a representative average saturation temperature of 40 ° C . Mass fluxes ranged from 300 to 800 kg ∕ m 2 s , and vapor qualities ranged from 0.85 to 0.95 at condenser inlet, to 0.05 to 0.15...

...Todd M. Bandhauer; Akhil Agarwal; Srinivas Garimella A model for predicting heat transfer during condensation of refrigerant R134a in horizontal microchannels is presented. The thermal amplification technique is used to measure condensation heat transfer coefficients accurately over small...