1American Institute of Aeronautics and Astronautics

AIAA-2003-0858

SIMULATION OF FLOW, HEAT TRANSFER & RELATIVE HUMIDITY CHARACTERISTICS IN AIR-CONDITIONED SURGICAL

OPERATING THEATRES

Ramiz Kameel†, Essam E. Khalil‡

Mechanical Engineering DepartmentFaculty of EngineeringCairo University, Egypt

ABSTRACTOne of the main objectives of ideal air distribution in heating, ventilation, and air

conditioning systems is to create proper combination of temperature, humidity, and air motion in the occupied zone of the air-conditioned room. Recent advances in air conditioning technologies and applications had led to better performance, development and modifications to air flow pattern in air conditioned rooms design for ultimate comfort, Berglund 1, Hosni et al. 2 and Medhat 3.

The healthcare requirements take different views depending on the air conditioning applications. The healthcare in residential applications is completely different than those in the medical applications, due to the nature of applications, and occupants. Pioneers in the medical applications enforced many restrictions to the comfort criteria requirements to form health criteria. These criteria were accumulated and compiled to healthcare standards such as ASHRAE standard for the residential and commercial applications and the National Health Service (NHS) standard for the healthcare applications.

Recent development of experimental measuring techniques for air temperature, relative humidity, velocities, and turbulence intensities in flow regimes had aided better understanding of flow phenomena, heat transfer and turbulence interactions. Extensive efforts are exerted to adequately predict the air velocity and turbulence intensity distributions in the room and to reduce the energy requirements and noise to ultimately produce quite and energy efficient air conditioning systems.

The present work fosters mathematical modeling techniques to primarily predict what happens in the air-conditioned surgical operating theatre in terms of flow regimes, heat transfer and their interactions. The governing equations of mass, momentum and energy are commonly expressed in the present finite difference form with source terms that represent pressure gradients, turbulence, viscous action, and heat transfer interactions. A full three-dimensional computational scheme, 3DHVAC, Khalil 4-6, Kameel 7,8, and Kameel and Khalil 9-11, was developed and used to predict the air flow regimes, relative humidity and heat transfer characteristics under actual room geometrical and operational conditions. The paper demonstrates the usefulness of utilizing such numerical procedures to adequately predict air-conditioned air behavior in operating theatres.

† Research Associate, M.Sc‡ Professor of Mechanical Engineering, M. ASME, ASHRAE, Associate Fellow AIAA

Copyright © 2003 by the American Institute of Aeronautics andAstronautics, Inc. All rights reserved.

41st Aerospace Sciences Meeting and Exhibit6-9 January 2003, Reno, Nevada

AIAA 2003-858

Copyright © 2003 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

2American Institute of Aeronautics and Astronautics

1. INTRODUCTION

Since the early sixties, many studies and researches concerned of the indoor air quality (IAQ) of healthcare applications. Hospital air conditioning resumes a more important role than just the promotion of comfort. In many cases, proper air conditioning is a factor in patient therapy; in some instance, it is the major treatment. Studies show that patient in controlled environments generally have more rapid physical improvement than do those in uncontrolled environments (ASHRAE, 1999) 12. Indoor air quality is more critical in health care facilities than in most other indoor environments due to many dangerous microbial and chemical agents present and due to the increased susceptibility of the patients, especially immunosuppressed persons (Healthy Buildings, 2000) 13.

The basic requirements in earlier studies were to achieve the aseptic conditions inside the healthcare applications and to control hazardous emissions for patients, personnel and visitors. The earlier studies were concerned of the optimum design of the ventilation system inside the hospitals to maintain the desired comfort and hygiene conditions.

Operating suite is the most critical area inside the hospital that requires special caring. The systems serving the operating rooms, including cystoscopic and fracture rooms, require careful design to minimize the concentration of airborne organisms. The largest amount of the bacteria found in the operating theatre comes from the surgical team and is a result of their activities during surgery. During an operation, most members of surgical team are in the vicinity of the operating table, creating the undesirable situation of contaminating in this highly sensitive area.

There are many surgical operating theatres worldwide with different architectural and air conditioning works designs. Exogenous sources of Surgical Suite Infection (SSI) pathogens include surgical personnel (especially members of

the surgical team), Calia et al 14, Dineen et al 15, Mastro et al 16, Ford et al 17, and Letts et al 18, the operating room environment including air, SSI 19, and all tools, instruments, and materials brought to the sterile filed during an operation. So, advances in infection control practices include improved operating room environment.

Studies of operating room air distribution devices and observation of installations in industrial clean rooms indicated that the supply of the air from the ceiling, with a downward movement to several extract ports located on opposite walls, is probably the most effective air movement pattern for maintaining the concentration of contamination at an acceptable level. Completely perforated ceilings, partially perforated ceilings, and ceiling-mounted diffusers have been applied successfully, Pfost 20. Surgical operating theatre suites are typically in use no more than 8 to 12 hr/day (excepting trauma and emergency departments). For energy conservation, the air conditioning system should allow a reduction in the air supplied to some or all the operating rooms when possible. Positive space pressure must be maintained at reduced air volumes to ensure sterile conditions. The time that required for an inactive room to become usable again must be considered. Consultation with the hospital surgical staff will determine the feasibility of this feature, ASHRAE 1999 12. A separate air extract system or special vacuum system should be provided for the removal of anesthetic trace gases, NIOSH 21. Medical vacuum systems have been used for removal of non-flammable anesthetic gases, NFPA standard 99 22. One or more outlets may be located in each operating room to permit connection of the anesthetic machine scavenger hose. Although good results have been reported from air disinfection of operating theatres by irradiation, this method is seldom used. The reluctance to se irradiation may be attributed to the need for special designs for installation, protective

3American Institute of Aeronautics and Astronautics

)1(S)grad-V(Div eff, ΦΦ =Φ⋅ΓΦρ

measures for patients and personnel, constant monitoring of lamp efficiency, and maintenance.

1.1. Purpose of Present WorkThe operating room environment depends

on, among others, the airflow velocity, turbulence level, temperature, and relative humidity. The improvement of the environment can be obtained by studying the air characteristics, experimentally or numerically. The drawback of the experimental methods is the time and the complicated equipment needed for the measurements especially in complex spaces such as operating theatres. On the other hand, CFD model can be a powerful tool to enhance the knowledge of the air characteristics Chow et al 23, Nielson 24. In the present study, 3DHVAC program developed by Khalil 4 and modified by Kameel 7-8, and Kameel and Khalil 9-11, is critically examined to adequately predict the airflow characteristics inside a complicated surgical operating theatre by Kameel 8, and Kameel and Khalil 25-27.

2. EXPERIMENTAL PROGRAMIn the New Kasr El-Aini Teaching

Hospital, the air conditioning system of surgical operating theatres was designed based on all air system, which supply all hospital zones by the clean air following the healthcare recommendations according to ASHRAE standards 12. Figure 1 represents a schematic layout of the surgical operating theatres under consideration, the figure represents the elevation view of the surgical operating theatre and the plan view of the same theatre. The Figure represents the positions of the supply air outlets relative to operating table, which was located in the center of the room. The room dimensions are 6.6 m in length (L), 4.0 m in width (WD), and 3.0 m in height (H). The operating table has a length of 2.0 m and a width of 0.5 m, and is 1.0 m high. Four ceiling square perforated supply air diffusers were located at the ceiling of the room with dimensions of 0.6 m x 0.6 m; their centers were located at

X, Y equal to (1.7,1.3), (4.9,1.3), (4.9,2.7), and (1.7,2.7) as shown in Figure 1. The extract ports were located on the left wall with dimensions of 0.5 m x 0.3 m and 0.5 m x 0.2 m; the lower port center point was located at 0.75 m from the floor. The higher return port center point was located at 2.25 m from the floor, Kameel 8.

3. NUMERICAL METHODS

3.1. Mathematical EquationsComputational Fluid Dynamics (CFD) is

used to model airflow by numerically solving equations based on fundamental physical principles. Three time averaged velocity components in X, Y, and Z coordinate directions were obtained by solving the governing equations using a "SIMPLE Numerical Algorithm" [Semi Implicit Method for Pressure Linked Equation] described earlier in the work, Spalding and Patankar 28, Launder and Spalding 29, and Khalil 30. The turbulence characteristics in the present work were represented by standard low-Reynolds k-εmodel to account for normal and shear stresses and near-wall functions. Fluid properties such as densities, viscosity and thermal conductivity were obtained from references. The present work made use of the Computer Program 3DHVAC, which was developed, by Khalil 4-6 and modified later by Kameel 7,8, and by Kameel and Khalil 9-11,17-19. The program solves the differential equations governing the transport of mass, three momentum components and energy in three-dimensional configurations. The different governing partial differential equations are typically expressed in a general form as:

The effective diffusion coefficients and source terms for the various differential equations are listed in Table 1. The Computational Fluid Dynamics (CFD) model utilizes the following approximations in calculating the turbulence quantities, such

4American Institute of Aeronautics and Astronautics

as isotropic turbulence and the Boussinesq eddy viscosity concept.

Table 1. Values of Φ, ΓΦ,eff, and SΦ for Partial Differential EquationsΦ ΓΦ,eff SΦ

Continuity 1 0 0X-momentum U µ - ∂P/∂x+ρgx

Y-momentum V µ - ∂P/∂y+ρgy

Z-momentum W µ - ∂P/∂z+ρgz+ρgβ∆tH-equation H µ / σH SH

RH-equation RH µ / σRH SRH

τ-age equation τ µ / στ ρµ = µlam + µ t

µ t = ρ Cµ k2 / ε

G = µ [2{(∂U/∂x)2 +(∂V/∂y)2 +(∂W/∂z)2}+(∂U/∂y + ∂V/∂x)2

+(∂V/∂z + ∂W/∂y)2 +(∂U/∂z + ∂W/∂x)2]C1 = 1.44, C2 = 1.92, Cµ = 0.09σH = 0.9, σRH = 0.9, στ = 0.9, σk = 1.0, σε = 1.3H-equation represents the Energy Equation.

3.2. Boundary ConditionsThe solution of the governing equations

can be realized through the specifications of appropriate boundary conditions. The values of velocity, temperature, kinetic energy, and its dissipation rate should be specified at all boundaries.

3.2.1 WallsA non-slip condition at all solid walls is

applied to the velocities. The logarithmic law of the wall (wall function) of Launder and Spalding 29 was used here, for the near wall boundary layer.

3.2.2. Air Supply InletsAt inlets, the air velocity was assumed to

have a uniform distribution; inlet values of the temperature were assumed to be of a constant value and uniform distribution. The kinetic energy of turbulence and its dissipation rate are commonly estimated as follow.kin = 3 (0.5 (Iin Uin)

2),εin = Cµ (kin)

1.5 / le,

3.2.3. Initial Guessed ValuesAll velocity components were set as zeros

initially, and temperatures were assumed to be equal to the steady state value of the comfort condition. The kinetic energy and its dissipation are estimated in the following manners.kinitial = 11E-5, εinitial = Cµ (kinitial)

1.5 / c ⋅ d,

3.3. Numerical ProcedureThe Computer Program, 3DHVAC of

Kameel and Khalil 9-11,17-19, was used to solve the time-independent (steady state) conservation equations together with the standard k-ε model as Launder and Spalding 29, and the corresponding boundary conditions. The numerical solution grid divided the space of the surgical operating theatre into discritized computational cells (80 x 60 x 30 grid nodes) using the modified hyperbolic equation of Kameel and Khalil 31, as in equation 2. The discrete finite difference equations were solved with the SIMPLE algorithm, Patankar 32. Solution convergence criteria, was applied at each iteration and ensured the summations of normalized residuals were less than 0.1% for flow, 1% for k and ε, and 0.1 for energy.

3.4. Models ValidationPrevious comparisons between measured

and predicted flow pattern, turbulence characteristics, and heat transfer was reported earlier in the open literature utilizing the present models. The predictions of flow and turbulence characteristics are in general qualitative agreement with the corresponding experiments and numerical simulations published by others, for further detail review, Kameel and Khalil 33-35.

4. PARAMETRIC CASESTwo operating theatre configurations are

shown in figure 2. The room dimensions are 6.0 m in length (L), 5.0 m in width (WD), and 3.0 m in height (H). The operating table has a length of 2.0 m and a width of 1.0 m, and is 1.0 m high. For the proposed design of first case study, ceiling square perforated supply air grilles were located at the center of the room with total dimensions 1.8 m x 1.8 m (9 modules of 0.6 m x 0.6 m with absolute filter banks), with partial walls, as shown in Figure 2. In the second case study, the air supplied from four separate

( ) ( )( ) ( ) )2(]

2/Cosh/2/Sinh

)5.0n/I(Cosh/)5.0n/I(Sinh

1[L5.0LX

11

i1i1

i1kk

αβα−αβ−α

++= −

5American Institute of Aeronautics and Astronautics

perforated diffusers; their locations are (1.3, 1.3), (4.7, 1.3), (4.7, 3.7), and (1.3, 3.7) m.

The extract ports were located on the left and right opposite walls, Figure 2. The extract grilles dimensions were 0.6 m x 1.8 m, located at 0.7 m from the floor, Kameel 8.

For the first case, the inlet supply discharge velocity was kept as 0.287 m/s and the second cases is 0.3 m/s and the air temperature was kept as 284 oK and the room temperature was taken as 296 oK for the two cases.

5. RESULTSIn this present work, a part of the

experimental results obtained in the surgical operating theatre will be shown, as a validation to the present model. The full experimental results are presented in details at Kameel 8, and Kameel and Khalil 33-35.

Measurements were obtained in the vicinity of the operating table between 1.0 m height and 2.0 m height from the floor. Figure 3 shows the measuring locations in both horizontal and vertical sections. During the experimental procedure the operating table was fixed in the geometrical center of the room floor.

As the operating theatre is the most important place in the hospital, while the operating area is the most important area in the operating theatres. The present section introduces the comparisons between measured and predicted results in the vicinity of the operating table. Figures 4 and 5 show the comparison of the temperature and relative humidity results respectively. The results are well identified and the predictions are in good trendwise agreement with the measurements although some differences in details exist. These comparisons gave a good indication about the present numerical model to predict the airflow characteristics in the vicinity of the internal objects. Figure 4 indicated the effect of the four supply diffusers located in the ceiling on the side ends of the operating table. The two longitudinal sides of the operating table at X = 2.3 m and X = 4.3 m have lower temperature than in the middle of

the operating table surface vicinity; such differences did not exceed the 0.5 oC. At the lower level of measurements, nearer to the table (i.e. 0.25 m above the operating table surface or 1.25 m above the floor), the air jet supplied from the ceiling diffusers had already spread to reach the area over the operating table. On the other hand, figure 5 showed the effect of the supply diffusers also on the side ends of the operating table. The two sides have higher relative humidity than the middle of the operating table. From the figures 4 and 5, it can be shown that the influence of the supply diffusers on the operating area is insignificant. The supply diffusers were designed to form protection curtains around the sides of the operating table.

The effect of using central supply diffusers covering the operating area and using four supply diffusers (0.6 x 0.6 m) is compared. The comparison between the two parametric cases is presented at the vertical line that passes across the center of the ceiling and the floor, as shown in figure 6.

From the figure 6, it can observe that the airflow in case 2 moves directly upward in the vicinity of the operating table. The upward flow appears a weak flow relative to the supply airflow, because the most supplied airflow consumed directly to create a curtain around the table without any real benefit to the operating area over the operating table. Design of case 1 is more efficient than the design of case 2.

The temperature distribution in the vicinity of the operating table of case 2 represents a pronounced similarity with relative humidity distribution. For the temperature distribution, the operating zone above the operating table was divided to three vertical zones. The first zone lies over the operating table surfaces, the second zone lies between the two levels (Z/H = 0.6 and 0.7), and the third zone lies closing to the ceiling. Three zones have the same criteria; the air temperature in each zone is almost constant. The relative humidity distribution has the same features of the temperature distribution. Both of temperature and

6American Institute of Aeronautics and Astronautics

relative humidity distributions are better in the case 2 than those distributions in case 1. Actually, the design of case 2 gave good temperature and relative humidity conditions in the operating area, but failed to create a downward flow in this area.

6. DISCUSSION AND CONCLUSIONIn the presented partially perforated

ceiling diffusers, case 2, the supplying system introduced the best thermal conditions with upward flow. Actually, the upward flow is completely refused in the operating theatre especially in the sterile zone (operating area). The upward flow in the operating zone is created from the horizontal inward air movement due to the partial impingement of the supply airflow with the operating table. The horizontal inward airflow goes toward the center of the operating table then goes upward, figure 7.The upward flow has several bad effects that can that can be described as follow:� The horizontal inward flow, which is the source of the upward flow, catches the airborne contamination from the patient and goes up to fill the zone of surgery staff breathing. This will aid of transferring the airborne contamination from the pollutant area to the clean area, which consequently will aid to increase the infection probability.� The pollutant upward flow goes to complete its recirculation cycle in the upper levels over the operating table to return back toward the supplied fresh clean air, which will aid also to increase the infection probability.� The recirculation cycle that is created from the upward flow over the operating area and the downward fresh flow from supply diffuses contributes to increase the contaminant concentration level that will be stored in the operating theatre, especially in the sterile zone.

7. RECOMMENDATIONSFrom preceding results, one can conclude

the importance of using one plenum supply covers the operating area. As mentioned earlier, one can conclude also the

effectiveness of the partial walls at the supply plenum to increase the efficiency of the downward airflow. Actually, also from previous discussion, it can conclude that themost optimum flow direction in the operating theatre and especially the operating area is the fully downward airflow. But according to the actual practice, the airflow should be horizontally in the vicinity of the operating table surface due to the impingement jet and the washing effect. So it recommended following the outward horizontal airflow over the operating table, not the inward horizontal airflow.

REFERENCES

1. Berglund, L. G., 1998, Comfort and Humidity, ASHRAE Journal, pp. 35-41, 1998.

2. Hosni, M. H., Tsai, K., and Hawkins, A. N., 1996, Numerical Predictions of Room Air Motion, Fluids Engineering Division Conference, Vol. ASME, pp. 745-751.

3. Medhat, A. M., 1993, Air Conditioning Flow patterns in Enclosures, M.Sc., Thesis, Cairo University.

4. Khalil, E. E., 1994, Three-Dimensional Flow Pattern in Enclosures, Interim Report, Egyptalum, Egypt.

5. Khalil, E. E., 1999, Fluid Flow Regimes Interactions in Air Conditioned Spaces, Proc.3 rd Jordanian Mech. Engineering Conference, Amman, May 1999.

6. Khalil, E. E., 2000, Computer Aided Design For Comfort In Healthy Air Conditioned Spaces, Proceedings of Healthy Buildings 2000, Finland, Vol. 2, Page 461-466.

7. Kameel, R., 2000, Computer Aided Design of Flow Regimes in Air Conditioned Spaces, M.Sc. Thesis, Cairo University.

8. Kameel, R., 2002, (In progress), Computer aided design of flow regimes in air-conditioned operating theatres, Ph.D. Thesis work, Cairo University.

7American Institute of Aeronautics and Astronautics

9. Kameel, R., and Khalil, E. E., 2000, Computer Aided Design of Flow Regimes in Air Conditioned Spaces, Proc. ESDA2000 ASME 5 th Biennial Conference on Engineering Systems Design & Analysis, Montreaux 2000.

10. Kameel, R., and Khalil, E. E., 2000, Fluid Flow and Heat Transfer in Air Conditioned Spaces, International Conference of Energy Systems, 2000, ICES, 2K. Page 188 –200, Amman, 25th

– 28th, Sept. 2000.11. Kameel, R., and Khalil, E. E., 2001,

Numerical Computations Of The Fluid Flow And Heat Transfer In Air-Conditioned Spaces, NHTC’01 1592, 35th National Heat Transfer Conference, June 10-12, 2001, Anaheim, California.

12. ASHRAE, Fundamentals, 1999, published by ASHRAE, Atlanta.

13. Healthy Building, 2000, Workshops, Workshop 22: IAQ in Hospitals, 2000.

14. Calia, F. M., Wolinsky, E., Mortimer, E. A. Jr., Abrams, J. S., Rammelkamp, C. H. Jr., 1969, Importance of the carrier state as a source of staphylococcus aureus in wound sepsis. J. Hyg. (London) 1969; 67:49-57.

15. Dineen, P., Drusin, L., 1973, Epidemics of postoperative wound infections associated with hair carriers, Lancet 1973; 2(7839): 1157-9.

16. Mastro, T. D., Farley, T. A., Elliott, J. A., Facklam, R. R., Perks, J. R., Hadler, J. L., et al., 1990, An outbreak of surgical wound infections due to group A streptococcus carried on the scalp, N. Engl. J. Med., 1990; 323:968-72.

17. Ford, C. R., Peterson, D. E., Mitchell, C. R., 1967, An appraisal of the role of surgical face masks, Am. J. Surg., 1967; 113:787-90.

18. Letts, R. M., Doermer, E., 1983, Conservation in the operating theatre as a cause of airborne bacterial contamination. J. Bone Joint Surg. [Am], 1983; 65:357-62.

19. SSI, 1999, Guideline for prevention of surgical site infection, Infection

control and hospital epidemiology, Vol. 20, No. 4, Jan 1999, USA.

20. Pfost, J. F., 1981, A re-evaluation of laminar airflow in hospital operating rooms, ASHRAE Transactions, Vol. 87(2): Page, 729-739.

21. NIOSH, 1975, Elimination of waste anesthetic gases and vapors in hospitals, Publication No., NIOSH 75-137, MAY, U.S. Dept. of Health, Education, and Welfare, Washington, DC.

22. NFPA, 1996, Standard for health care facilities. ANSI/NFPA standard 99-96.

23. Chow, T. T., Ward, S., Liu, J. P., and Chan, F. C. K. 2000, Airflow in hospital operating theatre: the Hong Kong experience, Proceeding of Healthy Buildings 2000, Vol. 2, Page 455-460.

24. Nielsen, P. V., 1989, Numerical Prediction of Air Distribution in Rooms, ASHRAE, Building Systems: Room Air and air Contaminant Distribution, 1989.

25. Kameel, R., and Khalil, E. E., 2001, Operating parameters affecting air quality in operating theatres: a numerical approach, Clima 2000/Napoli 2001 World Congress – Napoli (I), 15-18 September 2001.

26. Kameel, R., and Khalil, E. E., 2001, Air quality appraisal in air-conditioned operating theatres: numerical analysis, Clima 2000/Napoli 2001 World Congress – Napoli (I), 15-18 September 2001.

27. Kameel, R., and Khalil, E. E., 2001, Air quality appraisal in air-conditioned spaces: numerical analyses, Proc.4th IAQVEC Conference, Changsha, China, Page 287-297.

28. Spalding, D. B., and Patankar, S. V., 1974, “A Calculation Procedure for Heat, Mass and Momentum Transfer in Three Dimensional Parabolic Flows”,Int. J. Heat & Mass Transfer, 15, pp. 1787.

29. Launder, B. E., and Spalding D. B., 1974, “The Numerical Computation of Turbulent Flows”, Computer Methods App. Mech., pp. 269-275.

8American Institute of Aeronautics and Astronautics

30. Khalil, E. E., 1978, “Numerical Procedures as a tool to Engineering Design”, Proc. Informative 78, Yugoslavia.

31. Kameel, R., and Khalil, E. E., 2002, Generation of the grid node distribution using modified hyperbolic equations, 40th Aerospace Sciences Meeting & Exhibit, Reno, Nevada, AIAA-2002-656, 12-15 January 2002.

32. Patankar, S. V. 1980, Numerical heat transfer and fluid flow, 1980 Hemisphere, WDC.

33. Kameel, R., and Khalil, E. E., 2002, Experimental investigations of airflow regimes in air-conditioned operating theatres, Roomvent 2002

34. Kameel, R., and Khalil, E. E., 2002,Predictions of flow, turbulence, heat transfer and humidity patterns in operating theatres, Roomvent 2002

35. Kameel, R., and Khalil, E. E., 2002,Predictions of turbulence behavior using k-ε model in operating theatres, Roomvent 2002

NOMENCLATURE

c Constantd Distance to nearest sidewall.LWDH

Room Length, mRoom Width, mRoom Height, m

Iin Intensity of disturbance at air inlet.k Turbulence kinetic energy, m2/s2.Le Dissipation length at air inlet.p Pressure, Pascal.SΦ Source term of entity Φ, Φ = U, V, W, …U,V,W Instantaneous components of velocity in

three directions, m/s.X,Y,Z Coordinate directions.

ε Turbulence dissipation rate.Φ Dependent variable.ΓΦ,eff Effective diffusion coefficient.

µ Absolute viscosity of air, kg/ms.ρ Density of air, kg/m3.

σ Effective Prandtl number.φ Normalized Relative Humidity

= (RHp-RHr/RHs-RHr)

θ Normalized Temperature= (Tp-Ts/Tr-Ts)

ϖ Normalized W velocity = (Wp/Wo)

Subscriptsi Inner room (related to return outlets).i,j,k Denoting Cartesian coordinate direction

takes the values of axes X, Y, Z.o Outlet Supply (related to supply).t Turbulent property.

9American Institute of Aeronautics and Astronautics

Figure 1: Layout and Photo of the Experimental Configuration

Case 1 Case 2

Figure 2: Layout of Parametric Cases Configuration

10American Institute of Aeronautics and Astronautics

Figure 3: Measuring Probes Locations

Y=1.75 m Y=1.75 m

Y=2.0 m Y=2.0 m

Y=2.25 m Y=2.25 mFigure 4: Temperature Comparisons Figure 5: Relative Humidity Comparisons

11American Institute of Aeronautics and Astronautics

Figure 6a: Non-dimensional Velocity vertical variation at the table centre

Figure 6b: Non-dimensional Air Temperature vertical variation at the table centre

Figure 6c: Non-dimensional relative humidity vertical variation at the table centre

Figure 7: Upward Flow in the Vicinity of Operating Table (Case 2)