Experimental Apparatus for the Determination of Condensation Heat Transfer Coefficient for R134a and R600a Flowing Inside Vertical and Horizontal Tubes Respectively

2009 ◽  
Author(s):  
Ahmet Selim Dalkilic¸ ◽  
O¨zden Ag˘ra
Keyword(s):  
Heat Transfer ◽  
Test Section ◽  
Cooling Water ◽  
Condensation Heat Transfer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mass Fluxes ◽  
Experimental Apparatus ◽  
Vertical Test

Determination of condensation heat transfer coefficients for HFC-134a in a 7 mm i.d. vertical smooth copper tube and R600a in a 4 mm i.d. horizontal smooth copper tube are experimentally investigated. The test sections are 1 m long horizontal and 0.5 m long vertical counter flow tube-in-tube heat exchangers with refrigerant flowing in the inner tube and cooling water flowing in the annulus. The experiments are performed at average qualities ranging between 0.1–0.99 for the horizontal test section and 0.67–0.99 for the vertical test section. The mass fluxes are ranging between 50–120 kg m−2s−1 and saturation temperatures are between 30–43 °C for the horizontal test section, the mass fluxes are around 29 kg m−2s−1 and saturation temperatures are between 30–36 °C for the vertical test section. The experimental apparatus are designed to capable of changing the different operating parameters such as mass flow rate and condensation temperature of refrigerant, cooling water temperature, and mass flow rate of cooling water etc and investigate their effect on heat transfer coefficients and pressure drops. The ex-proof diaphragm pump for R600a and the gear pump for R134a are used to circulate the refrigerant in these systems. The detailed description of design and development of the test apparatus, control devices, instrumentation, and the experimental procedure are reported and the study of experimental setups from the available literature survey with the existing ones are compared in this paper. The condensation heat transfer coefficients are obtained for two different test sections with various experimental conditions and compared with some well-known correlations in the literature.

Measurement of Heat Transfer and Pressure Drop During Condensation of Carbon Dioxide in Microscale Geometries

2010 ◽  
Author(s):  
Brian M. Fronk ◽  
Srinivas Garimella
Keyword(s):  
Heat Transfer ◽  
Carbon Dioxide ◽  
Pressure Drop ◽  
Test Section ◽  
Copper Substrate ◽  
Condensation Heat Transfer ◽  
Heat Transfer Analysis ◽  
Transfer Coefficients ◽  
Local Pressure ◽  
Heat Transfer Coefficients

Heat transfer coefficients and pressure drops during condensation of carbon dioxide (CO2) are measured in small quality increments in microchannels of 100 < Dh < 200 μm. Channels are fabricated on a copper substrate by electroforming copper onto a mask patterned by X-ray lithography, and sealed by diffusion bonding. The test section is cooled by chilled water circulating at a high flow rate to ensure that the thermal resistance on the condensation heat transfer side dominates. A conjugate heat transfer analysis in conjunction with local pressure drop profiles allows driving temperature differences, heat transfer rates, and condensation heat transfer coefficients to be determined accurately. Heat transfer coefficients are measured for G = 600 kg m−2 s−1 for 0 < x < 1 and multiple saturation temperatures. Preliminary results for a 300 × 100 μm (15 channels) test section are presented. These data are used to evaluate the applicability of correlations developed for larger hydraulic diameters and different fluids for predicting condensation heat transfer and pressure drop of CO2.

Heat Transfer in Gas-Solids Drag-Reducing Flow

1985 ◽  
Vol 107 (3) ◽  
pp. 570-574 ◽  
Author(s):  
R. S. Kane ◽  
R. Pfeffer
Keyword(s):  
Heat Transfer ◽  
Test Section ◽  
Particle Deposition ◽  
Reynolds Numbers ◽  
Viscous Sublayer ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Vertical Tubes ◽  
The Heat Transfer Coefficient ◽  
Vertical Test

Heat transfer coefficients of air-glass, argon-glass, and argon-aluminum suspensions were measured in horizontal and vertical tubes. The glass, 21.6 and 36.0-μ-dia particles, was suspended at gas Reynolds numbers between 11,000 and 21,000 and loading ratios between 0 and 2.5. The presence of particles generally reduced the heat transfer coefficient. The circulation of aluminum powder in. the 0.870-in.-dia closed loop system produced tenacious deposits on protuberances into the stream. In the vertical test section, the Nusselt number reduction was attributed to viscous sublayer thickening; in the horizontal test section to particle deposition.

Representative Results for Condensation Measurements at Hydraulic Diameters ∼100 Microns

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Akhil Agarwal ◽  
Srinivas Garimella
Keyword(s):  
Heat Transfer ◽  
Test Section ◽  
Copper Substrate ◽  
Saturation Temperature ◽  
Electric Heater ◽  
Transfer Coefficients ◽  
Local Pressure ◽  
Pressure Drops ◽  
Heat Transfer Coefficients ◽  
Mass Fluxes

Condensation pressure drops and heat transfer coefficients for refrigerant R134a flowing through rectangular microchannels with hydraulic diameters ranging from 100 μm to 200 μm are measured in small quality increments. The channels are fabricated on a copper substrate by electroforming copper onto a mask patterned by X-ray lithography and sealed by diffusion bonding. Subcooled liquid is electrically heated to the desired quality, followed by condensation in the test section. Downstream of the test section, another electric heater is used to heat the refrigerant to a superheated state. Energy balances on the preheaters and postheaters establish the refrigerant inlet and outlet states at the test section. Water at a high flow rate serves as the test-section coolant to ensure that the condensation side presents the governing thermal resistance. Heat transfer coefficients are measured for mass fluxes ranging from 200 kg/m2 s to 800 kg/m2 s for 0< quality <1 at several different saturation temperatures. Conjugate heat transfer analyses are conducted in conjunction with local pressure drop profiles to obtain accurate driving temperature differences and heat transfer coefficients. The effects of quality, mass flux, and saturation temperature on condensation pressure drops and heat transfer coefficients are illustrated through these experiments.

Channel Size Based Measurement Techniques for Condensation Heat Transfer Coefficients in Mini- and Micro-Channels

2005 ◽  
Author(s):  
Srinivas Garimella ◽  
Akhil Agarwal ◽  
Todd M. Bandhauer
Keyword(s):  
Heat Transfer ◽  
Thermal Resistance ◽  
Flow Rate ◽  
Test Section ◽  
High Flow ◽  
High Flow Rate ◽  
Condensation Heat Transfer ◽  
Large Temperature ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients

A set of techniques for the measurement of condensation heat transfer coefficients for circular and noncircular channels with 5 mm &gt; Dh &gt; 100 μm is presented. For the larger range of Dh (5 &gt; Dh &gt; 0.4 mm), single tubes or multiple parallel extruded channels are used as test sections. The test section is cooled using water at a high flow rate to ensure that the condensation side presents the governing thermal resistance. Heat exchange with a secondary cooling water stream at a much lower flow rate is used to obtain a large temperature difference, which is used to measure the condensation duty. Condensation heat transfer coefficients are measured in small quality increments for 0 &lt; x &lt; 1 over the mass flux range 150 &lt; G &lt; 750 kg/m2-s with uncertainties typically less than 20%. For 200 &gt; Dh &gt; 100 μm, channels are fabricated on a copper substrate by electroforming copper onto a mask patterned by X-ray lithography, and sealed by diffusion bonding. Subcooled liquid is electrically heated to the desired quality, followed by condensation in the test section. Downstream of the test section, another electric heater is used to heat the refrigerant to a superheated state. Energy balances on the pre-and post-heaters establish the refrigerant inlet and outlet states at the test section. Water at a high flow rate serves as the test section coolant to ensure that the condensation side presents the governing thermal resistance. Heat transfer coefficients are measured for 200 &lt; G &lt; 800 kg/m2-s for 0 &lt; x &lt; 1. It is demonstrated that uncertainties as low as 6% can be achieved in the measurement of condensation heat transfer coefficients.

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.

Heat Transfer During Condensation of a Low-GWP Refrigerant on an Enhanced Cylindrical Surface

2017 ◽  
Author(s):  
Tailian Chen
Keyword(s):  
Heat Transfer ◽  
Smooth Surface ◽  
Cooling Water ◽  
Saturation Temperature ◽  
Condensation Heat Transfer ◽  
Condensation Process ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Cylindrical Tubes ◽  
Enhanced Tube

In this work, heat transfer coefficients during condensation of an environment-friendly refrigerant R-1233zd(e) on the outside surface of two cylindrical tubes are individually measured. The cooling water flows inside the tubes and provides cooling to the vapor refrigerant. One tube is a plain smooth tube (smooth both inside and outside) while the other tube is an enhanced tube, with the inside surface having 2D helical ridges and the outside surface having 3D extruded fins. The tests were conducted at the saturation temperature 36.1 °C, a typical temperature in chiller condensers. The results show the overall heat transfer coefficients of the enhanced tube are approximately 8.4 times higher as a result of the heat transfer enhancement on both sides. The condensation heat transfer degrades with an increase in the degree of subcooling, and the trend of degradation is the nearly the same for both the smooth and the enhanced tube, both is smaller than that in the Nusselt correlation. Compared with condensation on the smooth surface, the condensation heat transfer from the enhanced surface is enhanced approximately 10.8 times higher than that on the smooth surface. In addition to enlarged heat transfer area of the extruded fins, the enhancement in the condensation heat transfer is partly attributed to a better condensate draining mechanism of the 3D-structured fins where surface tension plays an important role. Further analysis reveals that heat transfer during the condensation process on the 3D low-fin surface follows the Nusselt correlation with a multiplier that accounts for the enhancement in heat transfer, which is desirably simple approach to modeling condensation heat transfer on the complex 3D enhanced surfaces. This work can lead to more insights into the physical mechanisms during the complex condensation process.

Condensation of R134a Flowing Inside Horizontal and Vertical Helicoidal Pipe

1999 ◽  
Author(s):  
H. J. Kang ◽  
C. X. Lin ◽  
M. A. Ebadian
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Water Flow ◽  
Heat Transfer Characteristic ◽  
Cooling Water ◽  
Transfer Characteristic ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mass Fluxes ◽  
Flow Reynolds Number

Abstract Condensing heat transfer characteristic of an ozone-friendly refrigerant HFC-R134a (Hydrofluorocarbon R134a) flowing inside a 12.7mm helicoidal tube was investigated experimentally to obtain heat transfer data and correlations. For this long helicoidal pipe at horizontal and vertical helicoidal positions, heat transfer measurements were performed for the refrigerant flow mass fluxes from 100 to 400 kg/m2/s, in the cooling water flow Reynolds number range of 1500 &lt; Rew &lt; 9000 at fixed system temperature (33°C) and cooling tube wall temperature (12°C and 22°C). Experimental results show that, with the increase of mass flux, the overall condensing heat transfer coefficients of R134a increase. However, with the increase of mass flux (or the cooling water flow Reynolds number), the refrigerant side heat transfer coefficients decrease. The effects of cooling wall temperature on heat transfer coefficients were considered. Predictive correlations valid over the above water flow Reynolds number ranges and refrigerant flow mass fluxes were proposed. Helicoidal pipe heat transfer characteristics were compared with data from literature reports for horizontal straight tube. Experimental results show that helicoidal pipe, especially at horizontal position, conducts a much better heat transfer characteristic than that of horizontal tube even it was grooved. The helicoidal pipe’s position plays a very great role on heat transfer characteristic with 100 percent higher results at a horizontal position than that of vertical position.

Measurement of Condensation Heat Transfer Coefficients in Microchannel Tubes

2001 ◽  
Author(s):  
Srinivas Garimella ◽  
Todd M. Bandhauer
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Test Section ◽  
Condensation Heat Transfer ◽  
Large Temperature ◽  
Liquid Region ◽  
Transfer Coefficients ◽  
Flow Rates ◽  
Heat Transfer Coefficients ◽  
Small Increments

Abstract A technique for the measurement of condensation heat transfer coefficients in microchannels is reported. The high heat transfer coefficients and low mass flow rates in microchannels make it difficult to accurately measure these coefficients. The requirements for accurate heat duty measurement are in direct conflict with the requirements for deducing the heat transfer coefficients from measured temperatures and flow rates. In addition, measurement of local condensation heat transfer coefficients in small increments of quality is difficult to accomplish due to the low heat transfer rates for such quality changes. The present work reports a technique that addresses these requirements. The inlet and outlet qualities to a microchannel test section are measured through energy balances on a pre- and post-condenser. The test section is cooled using water at a high flow rate to ensure that the condensation side presents the governing thermal resistance. Heat exchange with a secondary cooling water stream at a much lower flow rate is used to obtain a large temperature difference, which is in turn used to measure the condensation duty. Local heat transfer coefficients are therefore measured in small increments for the entire saturated vapor-liquid region. This technique is demonstrated using a square microchannel geometry with a hydraulic diameter of 0.76 mm. Heat transfer coefficients for the condensation of refrigerant R134a in this geometry range from 2,110–10,640 W/m2–K over the mass flux range 150 &lt; G &lt; 750 kg/m2–s.

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