exhibited a significant increase in the effectiveness and NTU of the heat
exchanger as the air bubbles were injected. It is suggested that the
disturbance and perhaps the turbulence intensity of the shell side flow are
increased due to the motion of air bubbles resulting in an increment in the
value of NTU and exergy loss
findings and correlations for the frictional two-phase pressure drops due to:
steam-water flow boiling, R-134a evaporation and condensation, air-water
two-phase flow and nanofluid flows are reviewed. Therefore, the purpose of
this study is to provide researchers in academia and industry with a
practical summary of the relevant correlations and supporting theory for the
calculation of the two-phase pressure drop in helically coiled tubes.
Dizaji et al. (2015)
experiments to study the effect of flow, thermodynamic and geometrical
characteristics on the exergy loss in a vertical shell and coiled tube heat
experimentally the effect of air bubble injection on the heat transfer rate
and effectiveness through a horizontal double pipe heat exchanger.
number of thermal units (NTU) and performance in a vertical shell and coiled
tube heat exchanger via air bubble injection into the shell side of heat
exchanger. Besides, exergy loss due to air bubble injection is investigated.
Indeed, air bubble injection and bubbles mobility (because of buoyancy force)
can intensify the NTU and exergy loss by mixing the thermal boundary layer
and increasing the turbulence level of the fluid flow
bubble flow rate, the microbubble swarm shows a significant pulsatory rise
along a vertical flat wall, particularly for small bubbles.
focus on an
increase in the effectiveness of a heat exchanger and analysis of various
parameters that affect the effectiveness of a heat exchanger and also deals
with the performance analysis of heat exchanger by varying various parameters
like number of coils, flow rate and temperature.
behavior depending on the parameter selected for the comparison with the base
condition according to the overall heat transfer coefficient for the whole
heat exchanger is found. Results indicate that the higher coil diameter, coil
pitch and mass flow rate in shell and tube can enhance the heat transfer rate
in these types of heat exchangers
purpose of this review summarizes the important published articles on the
enhancement of the convection heat transfer in heat exchangers using
nanofluids on two topics. The first section focuses on presenting the
theoretical and experimental results for the effective thermal conductivity,
viscosity and the Nusselt number reported by several authors. The second
section concentrates on application of nanofluids in various types of heat
exchangers: plate heat exchangers, shell and tube heat exchangers, compact
heat exchangers and double pipe heat exchangers.
thermo-physical properties of the working fluids were extremely temperature
dependent; therefore, rough correlations were proposed to predict their