ME598 Electronics Cooling – Fall 2024
Homework #6 - Heat Pipe Performance Calculations
• Assignment Date: Monday, 11/4/24
• Due Date: Monday, 11/11/24
• This homework is a practicing assignment for Topic 4 - Thermal Design of Microelectronics Systems with Heat Pipe Technology.
• We have gone over the following example problem in class today:
A sodium heat pipe with a wall thickness of 0.8mm has a pore radius rc of 3.17 x10-6mand a permeability, K of 1.43x10-11m2 and it operates at 600°C. The heat pipe geometries are shown below. What is the maximum heat load can transport due to the capillary limit when operating horizontally?
• For the sodium heat pipe example problem that we discussed in class. We have shown in
class the maximum heat load, Qmax, that the heat pipe can transport due to the capillary limit when operating horizontally.
1. Calculate Qmax value when operating gravity-aided (∅ = -90 ) and against gravity (∅ = +90 ).
Please note that ∅ is the operating angle of the heat pipe, do not confuse it with the contact angle,
θ which is always assumed to be zero (fully wet wick) in our calculations (10 points).
2. Calculate the pressure drop in the wick and the pressure drop in the vapor core under three operating orientations: horizontal, gravity-aided and against gravity. Show the percentage contribution of each pressure drop component to the total pressure drop (15 points).
3. Calculate the Reynolds number of the vapor flow at each operating orientation and determine if the flow is laminar or turbulent (15 points).
4. Calculate the Mach number of the vapor flow at each operating orientation and determine if the flow has reached sonic limit (15 points).