A Numerical Study of Flow Boiling Heat Transfer of Nanoemulsion in Mini-Channel Heat Exchanger

2018 ◽  
Author(s):  
Jiajun Xu ◽  
Musa Acar ◽  
Naresh Poudel ◽  
Jaime Rios ◽  
Thanh N. Tran
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Boiling Heat Transfer ◽  
Single Phase ◽  
Numerical Study ◽  
Flow Boiling ◽  
Heat Transfer Fluid ◽  
Working Fluid ◽  
Vof Model ◽  
Flow Boiling Heat Transfer

In this study, a numerical study has been performed on the two-phase heat transfer of a new nanostructured heat transfer fluid: Water-in-Polyalphaolefin (PAO) Nanoemulsion Fluid inside a mini-channel heat exchanger using ANSYS FLUENT. Nanoemulsion fluids are liquid suspensions of nanosized droplets, which are part of a broad class of colloidal dispersions. The nanoemulsion fluid can be formed spontaneously by self-assembly, in which these nanodroplets are in fact swollen micelles. To simplify the complexity of the numerical model, the nanoemulsion fluid was then treated as a homogenous fluid during single-phase and only the water vaporizes during the phase change. The volume of fraction (VOF) model with Pressure-Velocity coupling based Semi Implicit Method for Pressure Linked Equations (SIMPLE) iterative algorithm is employed to solve the continuity, momentum, energy equations in two dimensional domains. The thermophysical properties of the nanoemulsion fluid were measured and used for the current simulation. The results were verified using the experimental results and has shown good agreement. This study has demonstrated the feasibility of simplyig the simulation of flow boiling heat transfer of this new heat transfer fluid through treating it as a homogenous fluid during single-phase convective heat transfer and separating the vapor phase of the nano-micelles during flow boiling. This study has also shown that this Water-in-PAO nanoemulsion could function as a good and alternative conventional working fluid in heat transfer applications.

Flow Boiling Heat Transfer of HFO-1234yf in a Plate-fin Heat Exchanger with Plain Fins

2021 ◽  
Vol 25 (4) ◽  
pp. 87-92
Author(s):  
Chang-Hyo Son ◽  
Jeong-In Yoon ◽  
Sung-Hoon Seol ◽  
Dong-Ik Kang
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Flow Boiling Heat Transfer

A Fundamental View of the Flow Boiling Heat Transfer Characteristics of Nano-Refrigerants

2012 ◽  
Author(s):  
Lorenzo Cremaschi
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Liquid Phase ◽  
Transfer Coefficient ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Working Fluid ◽  
Heat Transfer Characteristics ◽  
Transfer Characteristics ◽  
Flow Boiling Heat Transfer

Driven by higher energy efficiency targets and industrial needs of process intensification and miniaturization, nanofluids have been proposed in energy conversion, power generation, chemical, electronic cooling, biological, and environmental systems. In space conditioning and in cooling systems for high power density electronics, vapor compression cycles provide cooling. The working fluid is a refrigerant and oil mixture. A small amount of lubricating oil is needed to lubricate and to seal the sliding parts of the compressors. In heat exchangers the oil in excess penalizes the heat transfer and increases the flow losses: both effects are highly undesired but yet unavoidable. This paper studies the heat transfer characteristics of nanorefrigerants, a new class of nanofluids defined as refrigerant and lubricant mixtures in which nano-size particles are dispersed in the high-viscosity liquid phase. The heat transfer coefficient is strongly governed by the viscous film excess layer that resides at the wall surface. In the state-of-the-art knowledge, while nanoparticles in the refrigerant and lubricant mixtures were recently experimentally studied and yielded convective in-tube flow boiling heat transfer enhancements by as much as 101%, the interactions of nanoparticles with the mixture still pose several open questions. The model developed in this work suggested that the nanoparticles in this excess layer generate a micro-convective mass flux transverse to the flow direction that augments the thermal energy transport within the oil film in addition to the macroscopic heat conduction and fluid convection effects. The nanoparticles motion in the shearing-induced and non-uniform shear rate field is added to the motion of the nanoparticles due to their own Brownian diffusion. The augmentation of the liquid phase thermal conductivity was predicted by the developed model but alone it did not fully explain the intensification on the two-phase flow boiling heat transfer coefficient reported in previous work in the literature. Thus, additional nano- and micro-scale heat transfer intensification mechanisms were proposed.

The Effect of Inlet Orifice on Critical Heat Flux and Flow Boiling Heat Transfer in Single Horizontal Microtube

2013 ◽  
Author(s):  
Yanfeng Fan ◽  
Ibrahim Hassan
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Critical Heat Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Saturation Pressure ◽  
Working Fluid ◽  
Flow Boiling Heat Transfer

Flow oscillation is a crucial issue for the development of flow boiling heat transfer in the applications. Inlet orifice has been proven be an option to eliminate the oscillation. However, the effects of inlet orifice on critical heat flux and flow boiling heat transfer coefficient are lack of study. In this work, the effects of inlet restriction on critical heat flux and heat transfer coefficient in single horizontal microtube under uniform heating condition is experimentally investigated using FC-72 as working fluid. A stainless steel microtube with an inner diameter of 889 μm is selected as main microtube. Two smaller microtubes are assembled at the inlet of main microtube to achieve the restriction configurations of 50% and 20% area ratios. The experimental measurement is carried out at mass fluxes ranging from 160–870 kg/m2·s and heat fluxes varying from 6–170 kW/m2. Two saturation pressures, 10 and 45 kPa, are tested. The experimental results of critical heat flux and two phase heat transfer coefficient obtained in the microtube without orifice are compared with the existing correlations. The addition of an orifice does not enhance the normal critical heat flux but increases the premature critical heat flux. In aspect of heat transfer, the orifice shows improvement on heat transfer coefficient at low mass flux and high saturation pressure.

Flow Boiling Heat Transfer Characteristics of a Minichannel Up to Dryout Condition

2009 ◽  
Author(s):  
Rashid Ali ◽  
Bjo¨rn Palm ◽  
Mohammad H. Maqbool
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Working Fluid ◽  
Flow Boiling Heat Transfer ◽  
The Heat Transfer Coefficient

In this paper the experimental flow boiling heat transfer results of a minichannel are presented. A series of experiments was conducted to measure the heat transfer coefficients in a minichannel made of stainless steel (AISI 316) having an internal diameter of 1.7mm and a uniformly heated length of 220mm. R134a was used as working fluid and experiments were performed at two different system pressures corresponding to saturation temperatures of 27 °C and 32 °C. Mass flux was varied from 50 kg/m2 s to 600 kg/m2 s and heat flux ranged from 2kW/m2 to 156kW/m2. The test section was heated directly using a DC power supply. The direct heating of the channel ensured uniform heating and heating was continued until dry out was reached. The experimental results show that the heat transfer coefficient increases with imposed wall heat flux while mass flux and vapour quality have no considerable effect. Increasing the system pressure slightly enhances the heat transfer coefficient. The heat transfer coefficient is reduced as dryout is reached. It is observed that dryout phenomenon is accompanied with fluctuations and a larger standard deviation in outer wall temperatures.

Flow Boiling Heat Transfer Characteristics of a Minichannel up to Dryout Condition

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Rashid Ali ◽  
Björn Palm ◽  
Mohammad H. Maqbool
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Mass Flux ◽  
Boiling Heat Transfer ◽  
Flow Boiling ◽  
Working Fluid ◽  
Flow Boiling Heat Transfer ◽  
The Heat Transfer Coefficient

In this paper, the experimental flow boiling heat transfer results of a minichannel are presented. A series of experiments was conducted to measure the heat transfer coefficients in a minichannel made of stainless steel (AISI 316) having an internal diameter of 1.70 mm and a uniformly heated length of 220 mm. R134a was used as a working fluid, and experiments were performed at two different system pressures corresponding to saturation temperatures of 27°C and 32°C. Mass flux was varied from 50 kg/m2 s to 600 kg/m2 s, and heat flux ranged from 2 kW/m2 to 156 kW/m2. The test section was heated directly using a dc power supply. The direct heating of the channel ensured uniform heating, which was continued until dryout was reached. The experimental results show that the heat transfer coefficient increases with imposed wall heat flux, while mass flux and vapor quality have no considerable effect. Increasing the system pressure slightly enhances the heat transfer coefficient. The heat transfer coefficient is reduced as dryout is reached. It is observed that the dryout phenomenon is accompanied with fluctuations and a larger standard deviation in outer wall temperatures.

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