July 2016 – Simulation Experts

Objective: The objective of this project was to verify the design of a ventilation system for the basement car parking area using CFD. The specific aim is to find the optimal locations, number & configuration of the induction fans required for the ventilation of the car parking lot, for the given positions of inlets and exhaust, and given configuration of the Supply air fans & exhaust fans, such that it meets requirements of CO exposure limit set by health & safety regulations and also to check whether it meets the sufficient visibility & temperatures in case of fire.

CO_ppm_1.7m_Withoutjet1.png — CO PPM Without Jet fans at 1.7 m

Technical Challenge: The acceptance contaminant level criterion for parking garages is specified in ASHRAE 2007 handbook. According to ASHRAE, the main criterion for car parks is that the carbon monoxide levels should remain below a designated peak value.

CO_ppm_1.7m_Withjet1.png — CO PPM with Jet fans at 1.7 m

Engineering Solution: The mathematical modelling using CFD can be developed which would simulate the actual behavior of the system. At first the analysis was done without placing any jet fans. This provides an indication of the stagnant areas in the car park. The subsequent analysis is done with jet fans operating so as to remove the stagnant areas , to reduce the concentrations of CO and to remove smoke in case of fire.

Velocity_vector_1.7m_Withoutjet1.png — Velocity Vectors at 1.7 m without Jet fans

Results and Conclusion:

The CO concentrations from the CFD simulations, without using induction fans has been obtained as 167.5 ppm which is higher than the safe CO limit for human beings.
After conducting CFD analysis by placing and optimizing the jet fans in the car park area, maximum CO level found to be as 27.8 ppm (33.36 mg/m3), which is with in safe CO limit for humans.
Ventilation System in the car park area has been designed optimally to reduce the CO level within the acceptable limits.
Velocity Vectors with Jet fans at 1.7 m

Objective: The objective of the project was to verify the hot water generator design by ensuring that the operation conditions are met based on actual experimental results of combustion, heat transfer and fluid flow through the combustion chamber and pipes. CFD Analysis was done to simulate the combustion and flow of hot flue gases through the combustion chamber, hot water generator and economizer till the exhaust and to calculate the temperature of water passing through the heat exchanger pipes as it comes out of the water outlet. Suggestions were given based on the simulation result to enhance turbulence in the fluid flowing inside the tube.

Modeling and Engineering Solutions: The proposed design uses the Lamont type hot water generator. The hot water generator has a rectangular box type construction which has an economizer over the top and it finally connects to the exhaust draft tube. The meshing scheme is used to distribute the mesh uniformly in the outer region and a very fine mesh in the central core region is used. The figure shows the geometry created and the meshing scheme used for this geometry.

Fig. Showing the Meshing scheme used for the Generator

Conclusion: After the analysis was done it was verified that the operating conditions of the hot water generator was similar to the actual experimental results of combustion, heat transfer and fluid flow through the combustion chamber and pipes. The total volume flow rate of water entering the hot water generator is 900 GPM. The economizer is designed to ensure that the water enters the inlet drums located at the bottom of the hot water generator at 160 F – 180 F. The temperature in the core combusting region is high and progressively reduces through the heat exchange region as it is carried away by the water and the flue gases. The positions of the baffles were clearly understood from the flow.