The Effect of Surface Thermal Radiation on Heat Transfer in a Ventilated Cavity

In this work, experimental and numerical results were obtained to analyze the effect of surface thermal radiation on heat transfer by mixed convection in a ventilated cavity. Experimental temperature profiles were obtained at six different depths and heights consisting of 14 thermocouples each. Five turbulence models were evaluated against experimental data. The radiative heat transfer model was solved with the discrete ordinate method. The effect of thermal radiation on experimental heat transfer coefficients is significant; it increases between 87% (Re = 30,372 and Ra = 3.04 × 1011) and 110% (Re = 6021 and Ra = 2.27 × 1011), when the emissivity of the walls increases from 0.03 to 0.98.

Experimental heat transfer studies on copper nanofluids in a plate heat exchanger

The objective of the present work is to study the influence of Copper nanoparticle concentration on heat transfer performance of mixed base fluid. In the present study, the performance of copper nanoparticles in (Ethylene Glycol (EG) + Propylene Glycol (PG) + Water (W)) base fluid was analyzed in the chevron-type Plate Heat Exchanger. The sol-gel method was used to prepare Copper nanoparticles (100 nm); dispersed in two different mixed base fluids of volume fractions 5%EG + 5%PG + 90%W and 15%EG +5%PG +80%W. Experiments were performed by varying the nanoparticle concentration from 0.2 to 1.0 vol %. Three different hot fluid inlet temperatures were used (55?C, 65?C and 75?C). It is revealed from the study that the rate of heat transfer increased significantly with the mixed base fluid. Result shows that at 75?C, 9%, and 14.9% enhancement in Nusselt number is obtained for 5%EG + 5%PG + 90%W and 15%EG +5%PG +80%W base fluid respectively for the nanoparticle concentration of 1%.

Thermal-hydraulic Assessment of Seven Wire-wrapped rod Bundle

Lead bismuth eutectic (LBE) is one of the most potential materials for coolant and spallation target for Accelerator Driven Systems (ADS). Thermal-hydraulic behavior of LBE in fuel assembly is a key issue for development of the systems. To get a deeper understanding on the complex thermal-hydraulic features of wire-wrapped rod bundle cooled by upward LBE, an electrically bundle with 7 rods wrapped with helical wire was developed in KYLIN-II thermal-hydraulic forced circulation loop. The flow resistance, thermal entrance characteristic and heat transfer coefficient were investigated. As for the entrance characteristics, during the full heating length (exceeding 140 times the hydraulic diameter), the thermal field did not reach a fully developed and stable condition which is contrary to the ducted flows. The experimental heat transfer coefficient showed that the hexagonal shell has a great influence on the heat transfer coefficient in rod bundle geometry. For this reason the application of empirical correlation should be kept cautious in rod bundle analysis.