scholarly journals Numerical simulation and analysis of phase change heat transfer in crude oil

2019 ◽  
pp. 464-464
Author(s):  
Ying Xu ◽  
Xin Nie ◽  
Zhonghua Dai ◽  
Xiao-Yan Liu ◽  
Yang Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Natural Convection ◽  
Crude Oil ◽  
Phase Change ◽  
Heat Release ◽  
Latent Heat ◽  
Breaking Point ◽  
Latent Heat Release ◽  
Waxy Crude Oil

Accurately obtaining the temperature distribution of the medium in the shutdown pipeline of waxy crude oil has important guiding significance for making maintenance plan and restart plan.The phase transition process of waxy crude oil involves complex problems such as natural convection heat transfer, latent heat release, difficulty in tracing liquid-solid interface. In this paper, the concept and significance of breaking point were proposed. Taking the breaking point and the freezing point as dividing point, and a new zonal partition model was established based on the influence of phase change of crude oil wax crystal on heat transfer mode, with the corresponding governing equations being established for different regions. With the proposed model, the effects of natural convection on heat transfer, latent heat release, location change of condensate reservoir, heat transfer mechanism and other key issues in the process of oil phase transition were analyzed.

Natural Convection in an Enclosure With Blend of Micro Encapsulated Phase Change Materials

2013 ◽  
Author(s):  
Yasmin Khakpour ◽  
Jamal Seyed-Yagoobi
Keyword(s):  
Heat Transfer ◽  
Thermal Expansion ◽  
Natural Convection ◽  
Phase Change ◽  
Latent Heat ◽  
Phase Change Materials ◽  
Numerical Study ◽  
Pure Water ◽  
Operating Conditions ◽  
Effective Density

This numerical study investigates the effect of using a blend of micro-encapsulated phase change materials (MEPCMs) on the heat transfer characteristics of a liquid in a rectangular enclosure driven by natural convection. A comparison has been made between the cases of using single component MEPCM slurry and a blend of two-component MEPCM slurry. The natural convection is generated by the temperature difference between two vertical walls of the enclosure maintained at constant temperatures. Each of the two phase change materials store latent heat at a specific range of temperatures. During phase change of the PCM, the effective density of the slurry varies. This results in thermal expansion and hence a buoyancy driven flow. The effects of MEPCM concentration in the slurry and changes in the operating conditions such as the wall temperatures compared to that of pure water have been studied. The MEPCM latent heat and the increased volumetric thermal expansion coefficient during phase change of the MEPCM play a major role in this heat transfer augmentation.

Heat transfer analysis of waxy crude oil under a new wide phase change partition model

2019 ◽  
Vol 76 (12) ◽  
pp. 991-1005
Author(s):  
Ying Xu ◽  
Xin Nie ◽  
Zhonghua Dai ◽  
Xiaoyan Liu ◽  
Yang Liu ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Crude Oil ◽  
Phase Change ◽  
Heat Transfer Analysis ◽  
Waxy Crude Oil ◽  
Partition Model ◽  
Waxy Crude

Experimental Study of Cylindrical Latent Heat Energy Storage Systems Using Lauric Acid as the Phase Change Material

2012 ◽  
Author(s):  
Chang Liu ◽  
Robynne E. Murray ◽  
Dominic Groulx
Keyword(s):  
Heat Transfer ◽  
Natural Convection ◽  
Energy Storage ◽  
Phase Change ◽  
Latent Heat ◽  
Storage Systems ◽  
Heat Energy ◽  
Hot Water ◽  
Energy Storage Systems ◽  
Water Flows

Phase change materials (PCMs) inside latent heat energy storage systems (LHESS) can be used to store large amounts of thermal energy in relatively small volumes. However, such systems are complicated to design from a heat transfer point of view since the low thermal conductivity of PCMs makes charging and discharging those systems challenging on a usable time scale. Results of experiments performed on both a vertical and a horizontal cylindrical LHESS, during charging, discharging and simultaneous charging/discharging, are presented in this paper. Both LHESS are made of acrylic plastic, the horizontal LHESS has one 1/2″ copper pipe passing through its center. The vertical LHESS has two 1/2″ copper pipes, one through which hot water flows, and the other through which cold water flows. Each of the pipes has four longitudinal fins to enhance the overall rate of heat transfer to and from the PCM, therefore reducing the time required for charging and discharging. The objective of this work is to determine the phase change behavior of the PCM during the operation of the LHESS, as well as the heat transfer processes within the LHESS. Natural convection was found to play a crucial role during charging (melting) and during simultaneous charging/discharging (in the vertical LHESS). However, during discharging, the effect of natural convection was reduced in both systems.

Effect of Microscale Mass Transport and Phase Change on Numerical Prediction of Freezing in Biological Tissues

2001 ◽  
Vol 124 (2) ◽  
pp. 365-374 ◽  
Author(s):  
Ramachandra V. Devireddy ◽  
David J. Smith ◽  
John C. Bischof
Keyword(s):  
Mass Transport ◽  
Phase Change ◽  
Heat Release ◽  
Latent Heat ◽  
Control Volume ◽  
Coupled Model ◽  
Biological Tissues ◽  
Freezing Process ◽  
Latent Heat Release ◽  
Biophysical Processes

A numerical model incorporating the microscale heat and mass transport in biological tissue during freezing is developed. The heat transfer problem is formulated in a general one-dimensional coordinate system (cartesian, cylindrical or spherical), and a finite control volume discretization is used. The latent heat release for each control volume in the domain is determined by the cellular water transport and intracellular ice formation processes occurring there (a coupled thermal/biophysical approach). The coupled model is applied to two cryobiological freezing problems, with different geometry and boundary conditions. The temperature dependent thermal properties of water and the biophysical properties of two biological tissues, normal rat liver and Dunning AT-1 rat prostate tumor tissue are used to simulate both the micro and macroscale freezing processes. A major advantage of the coupled thermal/biophysical model is its unique ability to predict both the macroscale thermal response and the microscale biophysical response at various locations within the tissue domain during a freezing process, simultaneously. Thermal histories predicted by the coupled model are compared to predictions of a standard enthalpy-method model in which the temperature dependence of the latent heat release, Λ(T) is an explicit function adapted from the water-NaCl phase diagram, and phase change is not rate-limited by microscale biophysical processes (i.e., an uncoupled approach). The results for both models are very similar; this suggests that the microscale biophysical processes which occur in the chosen biological tissues during freezing do little to limit the rate at which phase change occurs. Additional simulations suggest that the predicted macroscale thermal history results are not significantly affected (<2 percent variation) even with significantly altered biophysical parameters (i.e., a factor of 100 times lower or higher), as long as the magnitude of the latent heat is constant.

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