16.The diagram shows the construction of the inner liner of a vacuum bottle. How does a vacuum bottle prevent the transfer
of thermal energy:
a. by conduction?
there is no metal to
conduct heat
b. by convection?
there
Vacuum
between Mirrored
glass walls
hot or cold
liquid
c.
by radiation?

Air is to be preheated by hot exhaust gases in a cross-flow heat exchanger before it enters the furnace. air enters the heat exchanger at 95 kpa and 20°c at a rate of 0.6 m^3/s. the combustion gases (cp = 1.10 kj/kg°c) enter at 160°c at a rate of 0.95 kg/s and leave at 95°c. determine the rate of heat transfer to the air and its outlet temperature.