18 May 2017

P.4.3.1 Heat transfer performance of solid sorption heat pipes with composite NaBr-NH3 as working pair


Solid sorption heat pipe (SSHP) which integrates heat and mass transfer with solid-gas sorption technology is
proposed in this paper. Composite sorbent with sorbate (ammonia) are chosen as the working pair to replace the
capillary structure (wick) and working fluid in conventional heat pipe (HP) thus the major limits of heat transfer
can be overcome. Three different amounts of ammonia (1.14 mol, 3.01 mol and 4.88 mol) filled in the SSHP are
tested under different heat source temperature (from 50oC to 90oC) and heat sink temperature (20oC and 25oC) in
order to investigate the overall heat transfer performance. Two modes are investigated, i.e. heating mode for
which the sorbent temperature increases and cooling mode for which the sorbent temperature decreases. The test
results indicate that SSHP with vertical arrangement is available and realistic for heat transfer process. The
maximum heat transfer quantity in sorbent section is gotten under the condition of heating temperature of 80oC
and cooling temperature of 20oC for cooling mode, and its value is 0.87 kW. In condenser section the heat
transfer between both modes, i.e. cooling mode and heating mode, is relatively close and the maximum heat flux
is 22.11 kW/m2 and 17.61 kW/m2 respectively. The sorbents with different sorption quantity are also studied and
compared which show that the maximum heat transfer quantity per unit molar ammonia is 400.29 W/mol,
corresponding to the heat flux in sorbent section 14.84 kW/m2.