Page 368 - Mechanical Engineers' Handbook (Volume 4)

5 Other Types of Heat Pipes 357

CONDENSER

ADIABATIC SECTION B C

C

1.00 mm EVAPORATOR 5.70 mm B

A

A
1.00 mm
CASE MATERIAL: COPPER OR SILVER
WORKING FLUID: ULTRAPURE WATER

CASE

WORKING
VAPOR
FLUID
A – A B – B C – C

Figure 14 Schematic of a micro heat pipe.

from the evaporator to the condenser increases if the condensing area is constant. However,
there are some applications where the evaporator or condenser temperature needs to be kept
constant with a varying heat input. The variable-conductance heat pipe is suitable for this
function design and its unique feature is the ability to maintain a device mounted at the
evaporator at a near constant temperature, independent of the amount of power being gen-
erated by the device. To keep the operating temperature independent of the heat input, the
whole conductance of heat pipe should be varied with the heat load. Figure 15 illustrates a
typical variable conductance heat pipe (VCHP). Comparing the conventional heat pipe, this
VCHP as shown in Fig. 15 includes a gas reservoir containing noncondensable gas. When

Adiabatic
Evaporator Condenser
Section

Figure 15 Schematic of a variable-conductance heat pipe.