دراسة عملية لانتقال الحرارة بالحمل الحر لصفيحة مستطيلة الشكل مسخنة بثبوت درجة الحرارة

الملخص EN

An experimental investigation to know the effect of inclination angle (Φ), perforation ratio (m) and heating level on the rate of heat transfer by natural convection from isothermal rectangular flat plate (with and without rectangular hole) with extension surface.

The experiments covered the laminar region with a range of Rayleigh number of order of 106 .

The experimental study included the manufacturing of four rectangular models of aluminum (125mm) length,(64mm) width and (10mm) thickness and perforation ratio (m=0.0,0.2&0.28) respectively with heater for each model, and manufacturing a device allow fine movement of the thermocouple in three dimensions above the models surface with a capability of inclination the models up to (180°) with horizon Practical Experiments achieved by using local measure method for finding the temperature gradient, thermal boundary layer thickness (δ) using thermocouples .The experiment has been done with variable inclination angle from horizon (0°, 30°, 90°, 145°&180°) and four heating level (Tw=50, 70, 90&110°C) in range of Grashof number (1.632×106≤ GrLo ≤5.973×106) for each model.

The results show that the boundary layer thickness (δ) decrease while the temperature gradient increase when Grashof number and perforation ratio (m) increase.

The boundary layer thickness (δ) for incline position facing upward is more than facing downward while the temperature gradient is less.

The average Nusselt number increases with the increase of inclination of plates facing upward to reach to the higher average Nusselt number at vertical position then decreases with increase of inclination of plates.

Also Average Nusselt number value increases with increase of perforation ratio and Grashof Number.