Combined Convection and Radiation Experiments

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F L O R I D A I N T E R N A T I O N A L UN I V E R S I T Y

Mechanical Lab
EMA 4909L
Section 01
Group 6

5/27/2010

SUMMER-A SEMESTER
2010
DR. BELLADI

Combined Convection and Radiation Experiments Exercise B – Force Convection over a Cylinder in Cross-Flow

Experiment 1

Homero Perez
Shiv Shaw
Kirk S. Harvey # 1348271
EML 4909L Mechanical Lab

Force Convection over a Cylinder in Cross-Flow

Table of Contents

Abstract4

Nomenclature5

Introduction6

Data & Results7

Analysis and Discussion9

Conclusion and Recommendations15

Appendix A17

Appendix B: Procedures18

APPENDIX C19

List of Figures
Figure 1: HT10X Heat Transfer Service Unit5
Figure 2: Temperature on Cylinder9
Figure 3: Nusselt Number vs. Reynolds Number10
Figure 4: Convection heat transfer coefficient at different velocities11 Figure 512
Figure 6: Impact Jet Apparatus17

List of Tables
Table 1: Constants7
Table 2: Experimental Data8
Table 3: Experimental Data8
Table 4: Theoretical Data8
Table 5: Percent Error13

Abstract

The purpose of this report is to present experimental data that demonstrate the relationship between air velocity and surface temperature for a cylinder subjected to forced convection. This experiment will also determine the effects of forced convection on heat transfer from the surface of a cylinder at varying air velocities and surface temperatures. The forced convection theory is based on the same principle of moving air over a surface to increase the heat transfer rate from a surface. Therefore a surface subjected to forced convection will have a lower surface temperature than the same surface subjected to free convection, for the same power input. The force convection will be provided by the air compressor on the apparatus. The heat transfer will also be accomplished by means of radiation heat transfer as heat will be absorbed by the surroundings.

The experiment is setup using (see figure1):
• HT10X Heat Transfer Service Unit
• HT14 Combined Convection and Radiation Accessory
• IFD3 PC Interface Console
• Compatible PC

The air compressor will be operated at fully open and the air velocity will be systemically reduced back to zero or a natural convection state. The cylinder will be heated to a prescribed temperature corresponding to a particular voltage (14 volts). With the flow stream fully open the surface temperature of the cylinder will be read at the T10 thermocouple. The T9 thermocouple will be place upstream of the heated cylinder and measure the temperature of the air. There will be a great difference in temperature between the two thermocouples. As the flow across the surface of the cylinder is slowed the surface temperature will increase.

[pic]
Figure 1: HT10X Heat Transfer Service Unit

Nomenclature

|SYMBOL |DESCRIPTION |UNITS | |As |Surface area of the cylinder |m2 | |Q |Heat loss |W | |h |heat transfer coefficients |W/m2K | |kf |conductivity of the air |W/m·K | |σ |Stefan Boltzmann constant |W/m2·K4 | |ε |Emissivity of surface |m/s | |D |Diameter of the cylinder |m | |Nu...
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