Application of CFD in C/R Design 胡石政 PERFORMANCE COMPARSION OF AXIAL FAN AND FAN-FILTER UNIT(FFU) TYPE CLEAN ROOMS BY CFD

Outline  INTRODUCTION  NUMERICAL METHODS  Airflow model  Boundary conditions  RESULTS AND DISCUSSION  CONCLUSIONS

INTRODUCTION  Recirculation systems currently account for about fifteen percent of the electrical consumption of a fab.  There are several types of air recirculation systems available for uni-directional clean rooms in practice including ： a. the axial fan type system b. the fan-filter unit (FFU) type system c. the recirculation air-conditioner type system

axial fan type system

fan-filter unit (FFU) type system

recirculation air-conditioner type system

Schematic diagram of the FFU

an axial fan’s performance curves

a FFU’s performance curves

non-uniformity of ULPA filter face velocity (NU) ratio of standard deviation of the velocity to the mean face velocity

Airflow model div (  V  -  ,eff grad  ) = S   : air density (kg/m3) ,eff : the effective diffusion coefficient (N.s/m2 ) V:the air velocity vector (m/s) S  : source term of the general fluid property  : any one of 1,u,v,w,k

The Case Setup CASEC/R TypeL(m)Hs(m)Hr(m) PfPf PpPp PsPs  P sys. eff PcPc 1Axial Fan V f 80V p 2 25V s 25V out 2 30V c 2 2Axial Fan V f 80V p 2 25V s 25V out 2 30V c 2 3Axial Fan V f 80V p 2 25V s 25V out 2 30V c 2 4Axial Fan V f 80V p 2 25V s 25V out 2 30V c 2 5FFU V f 80V p 2 NN4V c 2 6FFU V f 80V p 2 NN6V c 2 7FFU V f 80V p 2 NN10V c 2 8FFU V f 80V p 2 NN20V c 2 Subscript ： r-return air chamber s-supply air chamber c-Dry coil p-Perforated floor f-ULPA filter s-Silencer & System effect of the axial fan

deflection angle (α)  Airflow deflection angle, α, in the working zone is affected by  ULPA face velocity non-uniformity  flow resistance across the perforated floors  clean room height  To adjust the α value by increasing the airflow resistance of the perforated floor may create too much resistance to the FFU resulting insufficient system flow rate

Comparison of system performance for axial fan type clean room and FFU type clean room CASE C/R Type L(m)Q t (m 3 /h)P s (Pa)P e (W) P e /Q t (W/CMM)  NU(%) 1 Axial Fan 24241, , Axial Fan , , Axial Fan , , Axial Fan 9.681, , Average152, , FFU24221, , FFU , , FFU , , FFU9.694, , Average158, , predicted power consumption per unit air quantity

Comparison of total annual charge for axial fan type clean room and FFU type clean room CASE Running CostHeat Load Cost Total Charge (NT$/year) Total Power Consumption (kWh/year) Currency Charge (NT$/year) Total Heat Load (kWh/year) Currency Charge (NT$/year) 1727, ,160144,754289, , ,440770,88076,737153,474924, ,480402,96040,11280,224483, ,740201,48020,05640,112241,592 Average353,685707,37070,414140,828848, ,075482,15047,99595,900578, ,224392,44839,06678,132470, ,620299,24029,80259,604358, ,915201,83020,09140,182242,012 Average171,958343,91634,23868,454412,370

Comparison of the predicted and experimental data Comparison of the predicted and experimental data

Velocity Vectors (m/s)  Axial Fan system  FFU system the FFU type system splits the system total flow volume to individual FFUs, the highest field velocity value of FFU system is lower than that of axial fan system.

Pressure distribution (Pa)  FFU system  Axial Fan system From the viewpoint of sealing work and filter installation/exchange, the FFU system is easier than that of axial fan system because the axial fan system exhibits a positive pressure in the SAP while the FFU system shows a negative one

CONCLUSIONS  For the first time, the fan performance curve was successfully input to the CFD model to investigate the operational characteristics of both the axial type clean room and the fan-filter unit (FFU) type clean room. The feasibility of such connection was verified and the predicted results were promising.  The performance of the FFU system examined is superior to that of the axial fan system based on the non-uniformity of the ULPA filter face velocity, deflection angle of airflow in the working zone, and energy consumption. However, more studies are required to understand the performance of these two systems to include the initial cost, the maintenance cost, the flexibility of space management etc.

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