Simulation model of a screw liquid chiller for process industries using local heat transfer integration approach

2005 ◽  
Vol 219 (2) ◽  
pp. 95-107 ◽  
Author(s):  
C. V. Le ◽  
P. K. Bansal ◽  
J. D. Tedford
Keyword(s):  
Heat Transfer ◽  
Simulation Model ◽  
Cooling Water ◽  
Local Heat Transfer ◽  
Load Ratio ◽  
Local Heat ◽  
Process Industries ◽  
Integration Approach ◽  
Shell And Tube ◽  
Tube Condenser

This paper presents a system simulation model of an oil-injected screw liquid chiller, where the refrigerant shell and tube heat exchangers are modelled following local heat transfer integration approach. All major components of the system are modelled in a modular format such as an oil-injected screw compressor, a shell and tube condenser, a flooded evaporator, and a high side-float valve. The simulation results are validated with the experimental data of a multiple-chiller plant at a process industry. The validated results show that the part-load ratio and the glycol-water temperature at the evaporator inlet affect the system performance considerably as compared to the temperature of cooling water entering the condenser.

The Simulation Study of Air Cooler in an Integrated Coal Gasification Combined Cycle System

2011 ◽  
Vol 354-355 ◽  
pp. 251-255
Author(s):  
Yan Li ◽  
Xiu Min Jiang ◽  
Jiang Wu ◽  
Jian Xing Ren
Keyword(s):  
Heat Transfer ◽  
Coal Gasification ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Combined Cycle ◽  
Tube Heat Exchanger ◽  
Cycle System ◽  
Porous Media Model ◽  
Air Cooler ◽  
Shell And Tube

A shell-and-tube heat exchanger which is widely used for the heat recovery of air in a coal gasification system is investigated. FLUENT6.3 software is used and the RNG k−ε turbulence model is adopted for modeling turbulent flow. The porosity rate, the distribution of the resistance and the distribution of the heat source were introduced to FLUENT by coupling the user defined function. The variation of local heat transfer is studied under the effects of the baffles arrangement. The result shows that the porous media model can be applied in shell side of the air cooler in IGCC and the reasonable arrangement of the baffles can decrease the pressure drop with little influence on the heat transfer.

Supercritical Heat Transfer and Pressure Drop in Refrigerant R410A

2003 ◽  
Author(s):  
Biswajit Mitra ◽  
Srinivas Garimella
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Pressure Drop ◽  
Transfer Coefficient ◽  
Cooling Water ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Coolant Temperature ◽  
Transfer Coefficients ◽  
Water Stream

This paper presents the results of an experimental study on heat transfer and pressure drop at critical and supercritical pressures of refrigerant R410A inside a horizontal 9.4 mm I.D. tube. Knowledge of heat transfer and pressure drop in such refrigerants blends at elevated pressures is gaining increasing attention for the design of vapor-compression space-conditioning and water heating systems at high heat rejection temperatures. Local heat transfer coefficients and pressure drops were measured for the mass flux range 200 < G < 800 kg/m2-s for the temperature range from 30–110°C. A technique that simultaneously allows accurate measurement of low local heat duties and deduction of the tube-side heat transfer coefficient from the measured overall resistance was used. A primary cooling loop using water at high flow rates ensures that the refrigerant side presents the governing thermal resistance. Heat exchange with a secondary cooling water stream at a much lower flow rate amplifies the coolant temperature difference, which in turn enables accurate heat duty measurements. The results show that the heat transfer coefficient exhibits a sharp peak in the vicinity of the vapor-liquid dome. These data are compared with the most relevant correlations from the literature and possible explanations for agreement and discrepancies between the data and predictions are provided.

Simulation and Experiment Study on Water Vapor Condensing Heat Transfer Characteristics in Horizontal Tubes

2016 ◽  
Author(s):  
Shengchun Liu ◽  
Jiahui Zhang
Keyword(s):  
Heat Transfer ◽  
Water Vapor ◽  
Simulation Model ◽  
Cfd Simulation ◽  
Local Heat Transfer ◽  
Horizontal Tube ◽  
Local Heat ◽  
Simulation And Experiment ◽  
Condensing Heat Transfer ◽  
Future Work

Water vapor condensing process inside horizontal tube has been studied in the paper. A CFD simulation model has been developed with Fluent software. An experimental investigation has also been conducted with an 8-mm inside diameter horizontal tube. As well as the heat transfer correlations available in literatures, the CFD model has been validated against the experimental results. The discrepancy of the simulation model is within 15%. The effect of wall temperature, inlet vapor velocity and inlet superheating degree on local heat transfer coefficient has been analyzed. The simulation model can be employed in future work to develop a condensation heat transfer correlation in horizontal tube.

Forced-Convective Condensation of Pure Steam and Ammonia-Steam Vapor Mixtures in a Shell-Tube Condenser

1999 ◽  
Author(s):  
Ratnesh K. Sharma ◽  
Vahab Hassani ◽  
Roop L. Mahajan
Keyword(s):  
Heat Transfer ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Ammonia Concentration ◽  
Transfer Coefficients ◽  
Average Heat ◽  
Heat Transfer Coefficients ◽  
Pure Steam ◽  
Convective Condensation ◽  
Tube Condenser

Abstract In this paper, we present our experimental findings for the forced-convective condensation of pure steam and ammonia-steam vapor mixture in a horizontal annulus in a counter-current shell-tube condenser. Experiments with ammonia-steam mixtures were conducted for ∼ 90% ammonia concentration (by wt.) for vapor inlet mass fluxes ranging from 2 to 5 kg/m2s. The local heat transfer coefficient varied considerably along the condenser and this variation was strongly linked to the condensate flow patterns in the annulus. Based on a condensate drainage model, the flow in the annulus was mapped on to flow maps for horizontal in-tube condensing flows. The delineated flow regimes were utilized to explain augmentation or deterioration of local heat transfer in the condenser. The average heat transfer coefficients are presented as a function of the condensate and vapor Reynolds number for both steam and ammonia-steam mixture. The results for pure steam are higher than those predicted by annular flow correlation developed in the past. For ammonia-steam mixtures, the average heat transfer coefficients are about 16% of those for pure steam due to the vapor layer resistance at the interface.

Local Condensation Heat Transfer Characteristics of Refrigerant R1234ze(E) Flow Inside a Plate Heat Exchanger

2017 ◽  
Vol 25 (01) ◽  
pp. 1750004 ◽  
Author(s):  
Mohammad Sultan Mahmud ◽  
Keishi Kariya ◽  
Akio Miyara
Keyword(s):  
Heat Transfer ◽  
Test Section ◽  
Cooling Water ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Plate Heat Exchanger ◽  
Heat Transfer Characteristics ◽  
Transfer Coefficients ◽  
Plate Heat ◽  
Heat Transfer Coefficients

In the present study, local condensation heat transfer coefficients of the R1234ze(E) inside a vertical plate heat exchanger (PHE) were investigated experimentally. In the experiment, three vertical flow channels are formed in the test section where refrigerant flows downward in the middle channel and cooling water flows upward in other two channels. The test section consists of eight plates: two of them form a channel of chevron type PHE for refrigerant flow channel, other two flat plates are set for heat transfer measurements, and another consist on cooling water flow channel. Down flow of the condensing refrigerant R1234ze(E) in the center channel releases heat to other channels of cooling water. In order to measure local heat transfer characteristics, a total of 60 thermocouples were set at middle of flow direction and also in the right and left sides of plates in test section. Experiments were conducted for mass fluxes ranging from 10[Formula: see text]kg/m2s to 50[Formula: see text]kg/m2s. The measurement results show that local heat transfer coefficients decrease with increase of wetness with different values in horizontal direction. Further, characteristics of local heat flux and wall temperature distribution as a function of distance from inlet to outlet of refrigerant channel were explored in detail.

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