Flow Analysis of Various Inlet Velocity Profiles on Indoor Temperature for Energy Conservation of HVAC System Using CFD

Energy conservation has been the most popular topic of the modern world. Heating, Ventilation and Air Conditioning (HVAC) systems consume approximately 10 % of the total energy of world. In order to improve the efficiency of HVAC systems, two dimensional (2D) room with inlet, outlet and heat source has been modeled. ANSYS Fluent has been used for numerical analysis of air flow in a 2D room. User Defined Functions (UDFs), which are coded in C language and hooked in ANSYS fluent, have been used for recording temperature variations and for heat generation within 2D room. Besides studying velocity fields and temperature distributions within indoor environment under specified boundary conditions, reference region for comparative analysis is also selected during Steady State (SS) numerical simulations. During transient analysis, temperature variations of a selected location are recorded for four different scenarios under varying inlet velocity profiles i.e. three for 0°, 30°, 60° angle with 1.3661 m/s velocity and fourth 0° with 2.7322 m/s velocity. Temperature profile of reference region after 1500 sec of transient simulations are compared with the steady state. Temperature profile of the scenario once the air is injected at 30° closely matched with the steady state temperature profile of the selected region. Time for attainment of SS temperature is also measured and compared after transient simulations. SS temperature value was attained twice, first at 240 seconds when the air was injected at 0° with 2.7322 m/s and secondly at 522 seconds when inlet air entered at velocity of 1.3361 m/s at 30°. The power consumption by increasing the fan speed is much higher as compared to the power consumed for changing direction only. Full Tex

Numerical Analysis of Impact of Relative Humidity on Crossflow Heat Exchangers with Staggered Configuration at Maximum Operating Temperature

Heat exchangers are employed in numerous applications of industry, automotive and air conditioning systems. The efficacy of heat exchangers depends upon various factors e.g., Reynolds number (Re) of the fluids, geometry of heat exchanging surfaces, and the Prandtl number of the cooling air. In this paper, the working of a crossflow heat exchanger with elliptical tubes is simulated numerically for 5000 < Re < 20000 at its maximum operating temperature of 323K. The tubes were arranged in a staggered way. The radical investigations were done at one-of-a-kind relative humidity ranges within the cooling air ranging from 0% to 80%. The relative humidity was modeled in the shape of mass fractions of water vapors in the air. The thermos-physical properties of dry and moist air were employed for the analysis. The impact of this changing of relative humidity on forced convection heat transfer of heat exchangers is examined in the form of percentage change in Nusselt number. With the increase in moisture content in the air, the Nusselt number was observed increased up to 4.5%. The paper provides a tool to analyze the Nusselt number of the elliptical-shaped heat exchanger while operating in moist atmospheric conditions. Full Tex

Flow Analysis of Various Inlet Velocity Profiles on Indoor Temperature for Energy Conservation of HVAC System Using CFD

Energy conservation has been the most popular topic of the modern world. Heating, Ventilation and Air Conditioning (HVAC) systems consume approximately 10 % of the total energy of world. In order to improve the efficiency of HVAC systems, two dimensional (2D) room with inlet, outlet and heat source has been modeled. ANSYS Fluent has been used for numerical analysis of air flow in a 2D room. User Defined Functions (UDFs), which are coded in C language and hooked in ANSYS fluent, have been used for recording temperature variations and for heat generation within 2D room. Besides studying velocity fields and temperature distributions within indoor environment under specified boundary conditions, reference region for comparative analysis is also selected during Steady State (SS) numerical simulations. During transient analysis, temperature variations of a selected location are recorded for four different scenarios under varying inlet velocity profiles i.e. three for 0°, 30°, 60° angle with 1.3661 m/s velocity and fourth 0° with 2.7322 m/s velocity. Temperature profile of reference region after 1500 sec of transient simulations are compared with the steady state. Temperature profile of the scenario once the air is injected at 30° closely matched with the steady state temperature profile of the selected region. Time for attainment of SS temperature is also measured and compared after transient simulations. SS temperature value was attained twice, first at 240 seconds when the air was injected at 0° with 2.7322 m/s and secondly at 522 seconds when inlet air entered at velocity of 1.3361 m/s at 30°. The power consumption by increasing the fan speed is much higher as compared to the power consumed for changing direction only. Full Tex

Numerical Analysis of Impact of Relative Humidity on Crossflow Heat Exchangers with Staggered Configuration at Maximum Operating Temperature

Heat exchangers are employed in numerous applications of industry, automotive and air conditioning systems. The efficacy of heat exchangers depends upon various factors e.g., Reynolds number (Re) of the fluids, geometry of heat exchanging surfaces, and the Prandtl number of the cooling air. In this paper, the working of a crossflow heat exchanger with elliptical tubes is simulated numerically for 5000 < Re < 20000 at its maximum operating temperature of 323K. The tubes were arranged in a staggered way. The radical investigations were done at one-of-a-kind relative humidity ranges within the cooling air ranging from 0% to 80%. The relative humidity was modeled in the shape of mass fractions of water vapors in the air. The thermos-physical properties of dry and moist air were employed for the analysis. The impact of this changing of relative humidity on forced convection heat transfer of heat exchangers is examined in the form of percentage change in Nusselt number. With the increase in moisture content in the air, the Nusselt number was observed increased up to 4.5%. The paper provides a tool to analyze the Nusselt number of the elliptical-shaped heat exchanger while operating in moist atmospheric conditions. Full Tex