ENME 332 STUDIO: HEAT CONVECTION EXPERIMENT Fall 2011 1209 Kim Building, Thermal Fluids Instructional Laboratory The objective of this experiment is to measure the convection heat transfer coefficient for a flat plate in a cross-flow of air and to compare the experimental results with the correlations. This experiment is also intended to help students better understand external flow heat transfer. A schematic of the test rig in this experiment is shown Figure 1. A flat plate (12.7cm in width and 15.2cm in length) with an internal cartridge heater is placed in an air flow produced by a wind tunnel. The plate surface temperature T s is measured by an attached thermocouple. The upstream air temperature T ∞ is assumed to be at the ambient room temperature. The velocity of the air flowing over the plate is calculated using measurements from a manometer (up to 100 mm H 2 O) and Bernoulli’s equation. Figure 1: Schematic of the convection apparatus.
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ENME 332 STUDIO: HEAT CONVECTION EXPERIMENT
Fall 2011
1209 Kim Building, Thermal Fluids Instructional Laboratory
The objective of this experiment is to measure the convection heat transfer coefficient for
a flat plate in a cross-flow of air and to compare the experimental results with the
correlations. This experiment is also intended to help students better understand external
flow heat transfer.
A schematic of the test rig in this experiment is shown Figure 1. A flat plate (12.7cm in
width and 15.2cm in length) with an internal cartridge heater is placed in an air flow
produced by a wind tunnel. The plate surface temperature Ts is measured by an attached
thermocouple. The upstream air temperature T∞ is assumed to be at the ambient room
temperature. The velocity of the air flowing over the plate is calculated using
measurements from a manometer (up to 100 mm H2O) and Bernoulli’s equation.
Figure 1: Schematic of the convection apparatus.
The heat transfer coefficient can be determined from Newton’s law of cooling:
q = h As (Ts - T∞)
where the power q is measured from the current and voltage across the heater, and Ts and
T∞ are temperature of the flat plate and the free stream air, respectively. These quantities
are known or can be measured. We will compare this experimental result with the
prediction from various correlations.
Experiment Instructions:
The lab group turns on the fan and then the cartridge heater. Record the plate
temperature as a function of time and indicate when steady state has been reached.
You need to answer the following questions in your lab report.
1) Plot the temperature Ts as function of time to see how it varies and to determine when
steady state is reached. Explain any oddities in your measurements.
2) Fill out the following table.
Run Voltage (V) Resistance
(Ω)
Manometer *
(mm H2O)
Air temperature
(°C)
Plate
temperature (°C)
1
3) What is the free stream air velocity? The air velocity can be calculated from the
Bernoulli Equation:
ZγVρ2
1pp 2
tot ++=
4) What is the power supplied to the heater?
5) What is the heat transfer coefficient h calculated from Newton’s law of cooling?
What is the corresponding Nu?
6) Evaluate Re and the Pr for your system condition. From your Re, what would you
expect your flow regime to be (i.e., would you expect your flow to be laminar or
turbulent)?
7) Compute Nu using the following correlation. How do the measured values of Nu