Research
Experimental and Numerical Model for Thermal Design of Air Cooled Condenser
The present work outlines a simple procedure for the thermal design of air cooled heat exchanger. The step by step numerical technique is implemented a long the steam flow direction to ratea vertical orientation single pass two tube rows heat exchanger. A saturated steam at atmospheric pressure of flow rate ranged between (18-36) kg/hr was passed throughout the tubes to provide a steam velocity in the range between (3.5) and (7) m/s. The condenser entering air dry bulb temperature was ranged between (21) and (42) oCand condensation load capacity fell in the range of (11) and (22.5) kW. The air flow rate was (1200) cfm and (2400) cfm corresponding air face velocities of (3 and 6) m/s. The simulated data showed excellent agreement with the measured rating parameters regarding the heat exchanger load duty and exit air cooling temperature. The respective discrepancy for the heat duty was within (12) % and (-5) % and the exit air temperature was underestimated by (5) %.
A Correlation for the Pool Boiling Enhancement Factor from Low Finned Tubes
The present work is devoted to formulate the enhancement factor of single enhanced, integrally machined finned tube boiling pure liquids in terms of active measures related to the boiling process. A new suggested correlation for the estimation of the nucleate pool boiling heat transfer coefficient was developed. The effects of the convective term due to the phase density differences and operating pressure on the boiling process were considered to stand independently. Eleven liquids, R-11, R-12, R-22, R-113, R-114,R123, R124, 134a, n-pentane, ethanol, water, boiling on the low finned tube, at different pressure for a heat flux in the range between (10) and (50) kW/m2 were considered. The total mean absolute error of the enhancement factors was (13.3%) for the whole range of data points. It was improved to be (10.8 %) for more than (95 %) of the data points. The correlation revealed its sensitive dependency for the enhancement factor on the parameters selected for its formulation. Most of the predicted enhancement factor values fell within (± 25) %deviation from the experimental data.
