1 American Institute of Aeronautics and Astronautics

Energy Efficient HVAC Design Applications in Hospitals

Prof. Dr. Essam E. Khalil Professor of Mechanical Engineering, Mechanical Power Engineering Department

Faculty of Engineering, Cairo University, Cairo, Egypt

I.ABSTRACT Hospitals and other healthcare facilities are complex environments that require special HVAC system design to achieve comfort and to control hazardous emissions. To build an effective HVAC system design to enhance the air quality in the healthcare facilities is a great challenge. The HVAC system is used to provide the required comfort level and in some cases for healing. Indoor Air Quality (IAQ) is more critical in healthcare facilities due to the hazardous microbial and chemical agents present and the increased susceptibility of the patients. The optimum Indoor Air Quality (IAQ) level is the responsibility of the architects and mechanical engineers. 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 has more rapid physical improvement than do those in uncontrolled environments. Although proper air conditioning designs are helpful in the prevention and treatment of disease, the application of air conditioning to health facilities presents many specific problems. Those are not encountered in the conventional comfort conditioning design. Air conditioning, therefore, includes the entire heat exchange operation as well as the regulation of velocity, thermal radiation and quality of air, as well as the removal of foreign particles and vapours. Health Consideration:

� The need to restrict air movement in and between the various departments (no cross movement). � The specific requirements for ventilation and filtration to dilute and reduce contamination in the form of odour, air-borne micro organisms and viruses, and hazardous chemical and radioactive substances.

� The different temperature and humidity requirements for various areas. � The design sophistication needed to permit accurate control of environmental conditions.

II.ENVIRONMENTAL CONTROL Temperature & Relative Humidity Control Codes and guidelines specify temperature range criteria in some hospital areas as a measure for infection control as well as comfort. Local temperature distributions greatly affect occupant comfort and perception of the environment. If the ambient indoor air temperature is too warm, people perceive the environment to be stuffy with little airflow. This condition can often result in fatigue and lethargy.

� The temperature should be controlled by change of supply temperature without any airflow control, � Temperature difference between the warm and cool regions should be minimized to decrease the airflow drift. � Good airflow distribution is required to create homogenous domain without large difference in the temperature distribution.

� Acceptable temperature in the occupancy zones and in the patient beds. Experimental Programs in the hospitals provides good information to assess the efficiency of the HVAC systems and provide a suitable guide for the maintenance engineers and the environmental engineers.Relative humidity affects human comfort directly and indirectly 1-10. It is a thermal sensation, skin moisture, discomfort, and tactile sensation of fabrics, health and perception of air quality. Low humidity affects comfort and health. Comfort complaints about dry nose, throat, eyes and skin occur in low humidity conditions, typically when the dew point is less than 2 oC. The upper humidity limit was a dew point of 17 oC in the ASHRAE 1-5, based not so much on comfort as on considerations of mold growth and other moisture related phenomena at lower levels of humidity, thermal sensation is a good indicator of overall thermal comfort and acceptability. But at high humidity levels, thermal sensation alone is not a reliable predictor of thermal comfort. The most proper conditions are between 35% and 50% 6-33. The laminar airflow concept developed for industrial clean room use has attracted the interest of some medical authorities. There are advocates of both vertical and horizontal laminar airflow systems. Laminar airflow in surgical operating theatres is airflow that is predominantly unidirectional when not obstructed. Laminar airflow has shown promising results in rooms used for the treatment of patients who are highly susceptible to infection. Among such

2nd International Energy Conversion Engineering Conference16 - 19 August 2004, Providence, Rhode Island

AIAA 2004-5591

Copyright © 2004 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved.

2 American Institute of Aeronautics and Astronautics

patients would be the badly burned and those undergoing radiation therapy, concentrated chemotherapy, organ transplants, amputations, and joint replacement. For high-contaminated areas, the local velocity should be greater than or at least equal to 0.2 m/s, which has back influence on the value of the supplied air to overcome this condition. For patient rooms 0.1 m/s is sufficient in the occupied area. The unidirectional laminar airflow pattern is commonly attained at a velocity of 0.45 ± 0.10 m/s.

Ventilation rates shall be in accordance with ASHRAE Standard 62-1989. Some facilities will have exhaust requirements that exceed required ventilation, and this will result in increasing outdoor air supply to balance the exhaust. Kitchen hood exhaust quantities dictate the quantity of supply air required for air conditioning. The entire system shall conform to the requirements of NFPA 96, Standard for ventilation of Restaurant Cooling Equipment. To conserve energy 80% of the hood's air requirement be provided by make-up air unit. A maximum of 50%-recirculated air shall be transferred from dining area to the kitchen and dishwashing areas. The dining areas shall be maintained at negative pressure relative to adjacent areas. Kitchen shall be maintained at negative pressure relative to dining areas. Air Change and Filtration Air filtration system will be designed to achieve indoor conditions comparable with ASHRAE Standards for similar types of buildings. Because of the widely fluctuating levels of atmospheric particulate due to sandstorms and duststorms, multistage filter system will be incorporated. Three basic filtration stages are usually incorporated namely:

� Primary filter to remove sand dust particles from the outside air prior to entering the air handling units in addition to filter made of pleated disposable located inside the air handling units.

� The second stage filter is the high efficiency particulate bag filter located in the air handling units with an efficiency of 80-85% based on ASHRAE Test Standard 52-1976.

� The third stage filter is the high efficiency particulate filter located at the air supply outlets high efficiency particulate absolute having an efficiency of 99.99% based on ASHRAE Test Standard 52-1976. Air Change per Hour (ACH) plays in important role to provide a free contamination place. The patient rooms are served by (2 ACH – 6 ACH) in usual. Some critical rooms could be served by value up to 12 ACH. The critical rooms, such as the surgical operating theatres, are supplied by (15 ACH – 25 ACH) in usual. There are some guidelines, which advise the value of 60 ACH for the critical areas. Actually the proper value of the ACH should improve the airflow distribution in the medical space. It was found, Kameel et al34-42 that the minimum value of ACH is 40 in the critical spaces to provide an optimum airflow distribution. Because of the dispersal of bacteria resulting from such necessary activities, air-handling systems should provide air movement patterns that minimize the spread of contamination. Undesirable airflow between rooms and floors is often difficult to control because of open doors, movement of staff and patients, temperature differentials, and stack effect, which is accentuated by the vertical openings such as chutes, elevator shafts, stairwells, and mechanical shafts common to hospital .The effect of others may be minimized by terminating shaft openings in enclosed rooms and by designing and balancing air systems to create positive or negative air pressure within certain rooms and areas see references [ 42-52] .Numerical procedures are conveniently used to predict local flow characteristics, see references [ 53-63]

Figure 1: Airflow Movement in Rooms The negative pressure is obtained by supplying less air to the area than is exhausted from it. This induces a flow of air into the area around the perimeters of doors and prevents an outward airflow. The operating room offers an example of an opposite condition. This room, which requires air that is free of contamination, must be positively pressurized relative to adjoining rooms or corridors to prevent any airflow from these relatively highly contaminated areas. In

3 American Institute of Aeronautics and Astronautics

general, outlets supplying air to sensitive ultraclean areas and highly contaminated areas should be located on the ceiling or on sidewalls closing to ceiling, figure 1, with perimeter or several exhaust inlets near the floor. This arrangement provides a downward movement of clean air through the breathing and working zones to the contaminated floor area for exhaust. The bottoms of return or exhaust openings should be at least 0.08 m. above the floor. Laminar airflow in surgical operating rooms is defined as airflow that is predominantly unidirectional when not obstructed. The unidirectional laminar airflow pattern is commonly attained at a velocity of 0.45±0.1 m/s.

III. DESIGN SPECIFICATIONS Hospital Facilities As, perfect air conditioning system is helpful in the prevention and treatment of disease, the construction of air conditioning system for health facilities presents many precautions not encountered in the usual comfort air conditioning systems. These precautions are;

(1) The need to restrict air movement in and between the various departments; (2) The specific requirements for ventilation and filtration to dilute and remove contamination in the form of

odour, airborne micro organisms and viruses, and hazardous chemical and radioactive substances; (3) The different temperature and humidity requirements for various areas; and (4) The design sophistication needed to permit accurate control of environmental conditions.

Specific Design Concept of Hospital Facilities There are seven principal divisions of an acute care hospital: (1) surgery and critical care, (2) nursing, (3) ancillary, (4) administration, (5) diagnostic and treatment, (6) sterilizing and supply, and (7) service. The environmental requirements of each of the departments/spaces within these divisions differ to some degree according to their function and the procedures carried out in them. Critical Care and Isolation Rooms In the isolation rooms for infectious patients, see Figure 1 , the patient bed should be located closing to the extraction ports. The infectious isolation rooms should be maintained in negative pressure, and located closing to positive pressure areas even in the part load of these areas. The immunosuppressed patient’s bed should be located in the side of supplied air, or close to the supply outlets, figure 2. See the work of Kameel and Khalil 34-43

Figure 2: Airflow Configurations for Critical Areas

Surgical Operating Rooms Operating room air distribution systems that deliver air from the ceiling, with a downward movement to several exhaust inlets located on opposite walls, is probably the most effective air movement pattern for maintaining the concentration of contamination at an acceptable level. For this reason and for energy conservation, the air-conditioning system should allow a reduction in the air supplied to some or all of the operating rooms. However, positive space pressure must be maintained at reduced air volumes to ensure sterile conditions, figure 3. It should be noted that this

4 American Institute of Aeronautics and Astronautics

figure indicated different air side designs for operating theatres; with ceiling mounted supply from a common module of outlets, or individual outlets or side wall supply air outlets. One or more extract outlets may be located in each operating room to permit connection of the anaesthetic machine scavenger hose, if any. The following conditions are recommended for operating, catheterization, cystoscopic, and fracture rooms:

1. There should be a variable range temperature capability of 20 °C to 24°C. 2. Relative humidity should be kept between 50% and 60%. 3. Air pressure should be maintained positive with respect to any adjoining rooms by supplying about 15% excess air. 4. Differential pressure indicating device should be installed to permit air pressure readings in the rooms. 5. Humidity indicator and thermometers should be located for easy observation. 6. Filter efficiencies should be in accordance with codes 7. Entire installation should conform to National Fire protection Agencies’ requirements for Health Care facilities. 8. All air should be supplied at the ceiling and exhausted or returned from at least two locations near the floor. Bottom of exhaust outlets should be at 0.08 m above the floor. Supply diffusers should be of the unidirectional type. High-induction ceiling or sidewall diffusers should be avoided.

9. Control centers that monitor and permit adjustment of temperature, humidity, and air pressure may be located at the surgical supervisor’s desk.

10. Conform to the fully vertical flow displacement (the present new hypothesis), or at least use one supply plenum in the center of the ceiling. The sidewall supplying is completely refused.

11. Use two opposite sidewalls as location of the extract grilles, it is more accurate to use the wide-distance opposite sidewalls as the extract walls. The supply plenum in this direction of the two opposite sidewalls can have the shorter side, figure 2. Keep the air extracting at two levels, one near the floor at level less than 1 m from the floor, and the other above the occupied zone and comfort level, i.e. 2 m from the floor.

12. It is essential to use partial walls in the upstream of the supplied air. 13. Leave two opposite sidewalls suitable for vertical extract duct shafts. This will allow the airside system designer to

follow the recommendations of positioning of the extract grilles in the suitable places.

Figure 3: Different Configurations of Surgical Operating Theatres42-49

5 American Institute of Aeronautics and Astronautics

14. Follow the recommended positioning of the operating table to let a one-bed length to the extract grilles. That will

aid to yield good airflow pattern around the operating table.

15. No medical equipment or surgery furniture should be placed close to the extract grilles to prevent the disturbance in the vicinity of the extract grille.

16. The surgical operating suite should be located in complete floor in the hospital, to be separated from the other suites and patient rooms, figure 4. In this figure the various rooms are located to form clean zones and indicated the supply and extract air routes.

Figure 4: Suggestion of Operating Suit Considering HVAC and Architectural Recommendations

Recovery Rooms Postoperative recovery rooms used in conjunction with the operating rooms should be maintained at temperature of 22°C and a relative humidity between 50% and 60%. Nursery Suite Air conditioning in nurseries provides the constant temperature and humidity conditions essential to care of the newborn in a hospital environment. Air movement patterns in nurseries should be carefully designed to reduce the possibility of drafts. All air supplied to nurseries should enter at or near the ceiling and be removed near the floor with the bottom of exhaust openings located at least 0.08 m above floor. Full-Term Nursery A temperature of 22°C and relative humidity from 30% to 60% are recommended for the full-term nursery, examination room, and work space. The maternity nursing section should be controlled similarly to protect the infant during visits with the mother. The nursery should have a positive air pressure relative to the workspace and examination room, and any rooms interposed between the nurseries and the corridor should be similarly pressurized relative to the corridor. This prevents the infiltration of contaminated air from outside areas.

6 American Institute of Aeronautics and Astronautics

Nursing Patient Rooms: Central systems should be used to air condition patients’ rooms, the recommendations for air filtration and air change rates should be followed to reduce cross-infection and to control odour 49. Rooms used for isolation of infected patients should have all air exhausted directly outdoors. A winter design temperature of 22°C with 30% RH is recommended; 22°C with 50% RH is recommended for summer. Each patient’s room should have individual temperature control. Egyptian governmental agency design criteria and international codes require that all air from toilet rooms be exhausted directly outdoors. Where room unit systems are used, it is important to exhaust through the adjoining toilet room an amount of air equal to the amount of outdoor air brought in the room for ventilation. Intensive Care Unit This unit serves seriously ill patients, from the postoperative to the coronary patient. A variable range temperature capability of 22°C to 27°C, a relative humidity of 30% minimum and 60% maximum, and positive air pressure are recommended. Protective Isolation Units Immunosuppressed patients are highly susceptible to diseases. An air distribution of 15 air changes per hour supplied through a nonaspirating diffuser is recommended. The sterile air is drawn across the patient and returned near the floor, at or near the door to the room. When the patient is immunosuppressed but not contagious, a positive pressure should be maintained between the patient room and adjacent area. Exam and treatment rooms should be controlled in the same manner. A positive pressure should also be maintained between the entire unit and the adjacent areas to preserve sterile conditions. When a patient is both immunosuppressed and contagious, isolation rooms within the unit may be designed and balanced to provide a permanent equal or negative pressure relationship with respect to the adjacent area or anteroom. So alternatively, such isolation rooms may be equipped with controls that enable the room to be positive, equal, or negative in relation to the adjacent area. However, in such instances, controls in the adjacent area or anteroom must maintain the correct pressure relationship with respect to the other adjacent room(s). Infectious Isolation Unit The infection isolation room is used to protect the remainder of the hospital from the patients’ infectious diseases. Recent multidrug-resistant strains of tuberculosis have increased the importance of pressurization, air change rates, filtration, and air distribution design in these rooms. Temperatures and relative humidity should correspond to those specified for patient rooms. The use of CFD techniques to predict the flow pattern, temperatures, relativ humidities and age of particulates was suggested by Khalil et al 49.

IV.CONCLUSIONS AND RECOMMENDATIONS The air is not just a medium but it can be regarded as a guard in the critical health applications. The airflow can be used as an engineering tool to provide “free contaminant” area. The proper direction of the airflow increases the possibilities of successful pollutant scavenging from healthcare applications. The proper airflow direction starts from the optimum design of the HVAC airside system and the optimum election of the supply outlets and extraction ports. The present work introduced a preliminary trail to find the optimum HVAC airside design in the healthcare facilities. The numerical tool, used here, was found to be so effective to predict the airflow pattern in the healthcare facilities at reasonable costs and acceptable accuracy. So it is recommended to use the CFD utilities as preliminary tools to explore the optimum HVAC airside design. Indeed, the optimum HVAC airside design starts from the architectural design of the healthcare facilities. Good architectural design allows the HVAC system designers to properly locate the supply outlets and extraction ports in the optimum locations. Critical areas and those of specific airflow, temperature and relative humidity requirements should be located in separate sections or departments. Indeed, in the larger hospitals, it is preferable to locate the critical areas in separate floors. Especially the surgical operating rooms should be located in separate suite. As for the already existing designs with poor airflow distribution, hospital environmental engineer should endeavour to improve the airflow pattern by redistributing the medical equipment and furniture in the proper location.

ACKNOWLEDGEMENTThe author would like to acknowledge the technical assistance of his colleagues and students.

7 American Institute of Aeronautics and Astronautics

REFERENCES

[1] AIA, 1996, Guidelines for design and construction of hospital and health care facilities, The American Institute of Architects, Washington, D. C. [2] Allen, D. E., 1979, Hospital planning – the development of the 1962 hospital plan – a case study in decision making, Pitman Medical. [3] ASHRAE, 2001, ASHRAE Handbook – Fundamentals, American Society of Heating, Refrigerating, and Air-Conditioning Engineers. [4] ASHRAE, 1997, Measuring Air-Change Effectiveness, ANSI/ASHRAE 129-1997, American Society of Heating, Refrigerating, and Air-Conditioning Engineers. [5] ASHRAE, Applications, 1999, pub. By ASHRAE, Atlanta. [6] ASHRAE, Fundamentals, 2002, published By ASHRAE, Atlanta. [7] Awbi, H. B., and Karimipanah, T., 2001, A comparison between three methods of low-level air supplies, Proceedings of the 4th International Conference on Indoor Air Quality, Ventilation & Energy Conservation in Buildings, Changsha, Hunan, Hong Kong, China. [8] Ayliffe, GA., 1991, Role of the environment of the operating suite in surgical wound infection, Rev Infect Dis 1991; 13 (Suppl 10): S800-4. [9] Berglund, L. G., 1998, Comfort and humidity, ASHRAE Journal, page 35 - 40, August 1998. [10] Blowers, R., and Crew, B., 1960, Ventilation of operating theatres. J Hyg 1960; 58:427-448 [11] Blum, H. M., 1956, Experimental verification of turbulence models, ASHRAE Transactions Vol. 1 pp. 30 published by ASHRAE, Atlanta, USA. [12] Cain, W. S., Samet, J. M., and Hodgson, M. J., 1995, The quest for negligible health risk from indoor air, ASHRAE Journal 37(7): 38. [13] Chen, Q., and Jiang, Z., 1996, Simulation of a complex air diffuser with CFD technique, Proc. of ROOMVENT '96, Vol. 1, pp. 227-234. [14] Chen, Q., and Moser, A., 1991, Simulation of a multiple-nozzle diffuser, Proc. of 12th AIVC Conference, Vol. 2, pp. 1-14. [15] Chen, Q., and Xu, W., 1998, A zero-equation turbulence model for indoor airflow simulation, Energy and Buildings, Vol. 28 (2), 137-144. [16] Chou, P. Y., 1945, On velocity correlations and the solution of the equations of turbulent fluctuations, Quart. Appl. Math. 3, 38. [17] 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, Vol. 2, Finland. [18] CR 1752, 1998, Ventilation for buildings: Design criteria for the indoor environment, CEN, Brussels. [19] Fang, L., Clausen, G., and Fanger, P. O., 1996, The impact of temperature and humidity on perception and emission of indoor air pollutants, Indoor Air’ 96, Tokyo, Institute of Public health. [20] Fanger, P. O., 1972, Thermal Comfort, McGraw-Hill, New York. [21] Han, H., Kuehn, T. H., and Kim, Y. I., 1999, Local mean age measurements for heating, cooling, and isothermal supply air conditions, ASHRAE Tans. Vol. 105, 275-282. [22] Han, X. V., and Chen, B, 2001, The interference of surrounding physical factors to IAQ subjective evolution, Proceedings of the 4th International Conference on Indoor Air Quality, Ventilation & Energy Conservation in Buildings, Changsha, Hunan, Hong Kong, China. [23] Healthy Buildings, 2000, Indoor Air Quality in Hospitals and Other Health Care Facilities, Workshops, Workshop 22, IAQ in Hospitals, Initiated by ISIAQ Task Force IV. [24] Holcatova, I., and Holcat, M., 1994, Indoor air quality and respiratory diseases, In Proceedings of Healthy [25] Hosni, M. H., Tsai, K., and Hawkins, A. N., 1996, Numerical predictions of room air motion, Fluids Engineering Division Conference. Vol. 2 ASME, Page. 745-751. [26] Humphreys, H., 1993, Infection control and the design of a new operating theatre suite, Journal of Hospital Infection 1993; 23: 61-70. [27] Hutchinson, P., Khalil, E. E., Whitelaw, J. H., and Wigley, G. 1976, The calculation of furnace-flow properties and their experimental verification, J. of Heat Transfer May 1976 page 276. [28] ISO EN 7730, 1994, Moderate thermal environments – Determination of the PMV and PPD indices and specification of the conditions for thermal comfort, International Standards Organization, Geneva. [29] Kameel, R., 2000, Computer aided design of flow regimes in air-conditioned spaces, M.Sc. Thesis, Cairo University. [30] Kameel, R., and Khalil, E. E., 2000 a, Computer aided design of flow regimes in air-conditioned Spaces, Proc. ESDA2000 ASME 5th Biennial Conference on Engineering Systems Design & Analysis, Montreaux 2000. [31] Kameel, R., and Khalil, E. E., 2000 b, 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. [32] Kameel, R., and Khalil, E. E., 2001 a, Numerical computations of the fluid flow and heat transfer in air-conditioned spaces, NHTC2001-20084, 35th National Heat Transfer Conference, Anaheim, California.

8 American Institute of Aeronautics and Astronautics

[33] Kameel, R., and Khalil, E. E., 2001 b, Operating parameters affecting air quality in operating theatres: a numerical approach, Clima 2000/Napoli 2001 World Congress – Napoli (I), 15-18 September 2001. [34] Kameel, R., and Khalil, E. E., 2001 c, Air quality appraisal in air-conditioned operating theatres: numerical analysis, Clima 2000/Napoli 2001 World Congress – Napoli (I), 15-18 September 2001. [35] Kameel, R., and Khalil, E. E., 2001 d, Air quality appraisal in air-conditioned spaces: numerical analyses, Proc.4th IAQVEC Conference, Changsha, China, Page 287-297. [36] Kameel, R., and Khalil, E. E., 2002 a, Generation of the grid node distribution using modified hyperbolic equations, 40th Aerospace Sciences Meeting & Exhibit, Reno, Nevada, AIAA-2002-656, 12-15 January 2002. [37] Kameel, R., and Khalil, E. E., 2002 b, Verification of numerical prediction of 3-D air-conditioned flow behavior in full and reduced scale room models, 40th Aerospace Sciences Meeting & Exhibit, Reno, Nevada, AIAA-2002-654. [38] Kameel, R., and Khalil, E. E., 2002 c, Prediction of airflow characteristics in air-conditioned surgical operating theatres, Proceedings of the Ninth Asian Congress of Fluid Mechanics, May, 27-31, 2002. Isfahan, Iran [39] Kameel, R., and Khalil, E. E., 2002 d, Numerical computations of flow, turbulence, heat transfer, and humidity patterns in surgical operating theatre, Proceedings of ESDA2002, 6th Biennial Conference on Engineering Systems Design and Analysis Istanbul, Turkey, July 8-11, 2002.[40] Kameel, R., and Khalil, E. E., 2002 e, Energy efficient air conditioning systems in hospitals operating theatres, IECEC 2002 Paper No. 20049, 2002. [41] Kameel, R., and Khalil, E. E., 2002 b, Experimental investigations of airflow regimes in air-conditioned operating theatres, 2002-122, Roomvent 2002. [42] Kameel, R., and Khalil, E. E., 2002 c, Predictions of flow, turbulence, heat transfer and humidity patterns in operating theatres, 2002-120, Roomvent 2002. [43] Kameel, R., and Khalil, E. E., 2002 d, Predictions of turbulence behavior using k-ε model in operating theatres, 2002-121, Roomvent 2002. [44] Kameel, R., Khalil, E. E., and Medhat, A. A., 2002, Assessment of a 3-D numerical predictions of air flow regimes in air-conditioned spaces using an experimental reduced scale model, 40th Aerospace Sciences Meeting & Exhibit, Reno, Nevada, AIAA-2002-653, 12-15 January 2002. [45] Khalil, A., Khalil, E. E., and Medhat, A. M., 2000, Experimental investigations of air conditioned room comfort, Proc. 9th AMME Conference on Applied Mechanics and Mechanical Engineering, Cairo 16-18 May 2000. [46] Khalil, E. E., 1978, Numerical procedures as a tool to engineering design, Proc. Informatica 78, Yugoslavia, 1978. [47] Khalil, E. E., 1980, Initial and boundary conditions and their influence on numerical computations of confined elliptic flows, Faculty of Engineering, Cairo University, 1980. [48] Khalil, E. E., 1994, Three-dimensional flow pattern in enclosures, Interim Report, Egyptalum, Egypt. [49] Khalil, E. E., and Kameel ,R (2004) Requirements Of Air-Conditioning Systems’ Developments In Hospitals and Critical Healthcare Facilities ESDA- 2004-58112 [50] Khalil , E.E. (1999) Fluid flow regimes interactions in air-conditioned spaces, Proc. 3 rd Jordanian Mech. Engineering Conference, Amman, May 1999. [51] 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. [52] Khalil, E. E., Spalding, D. B., and Whitelaw, J. H., 1975, The calculation of local flow properties in two-dimensional furnaces, Int. Heat & Mass Transfer, Vol. 18, Page 775. [53] Launder, B. E., Reece, G. J., and Rodi, W., 1975, Progress in the development of Reynolds stress turbulence closure, J. Fluid Mechanics, 68, 537. [54] Launder, B. E., and Spalding D. B., 1974, The numerical computation of turbulent flows, computer methods, App. Mech., Page. 269-275. [55] Launder, B. E., and Spalding, D. B., 1972, Mathematical models of turbulence, Academic Press, London. [56] Launder, B. E., and Spalding, D. B., 1973, The numerical computations of turbulent flows, Imperial College, Dept. of Mech. Eng. Report HTS/73/2, see also Computer Methods in Applied Mechanics and Engineering, 3. 269, 1974. [57] Lee, H., and Awbi, H. B., 2001, Internal partitioning and air movement in mixing ventilation, Proceedings of the 4th International Conference on Indoor Air Quality, Ventilation & Energy Conservation in Buildings, Changsha, Hunan, Hong Kong, China. [58] Medhat, A.M. 1993, Air Conditioning Flow patterns in Enclosures, M.Sc. Thesis, Cairo University, 1993. [59] Medhat, A.M., 1999, Optimizing room comfort using experimental and numerical modeling, Ph.D. Thesis, Cairo University, 1999. [60] Memarzadeh, F., and Manning, A., 2001, Thermal comfort, uniformity, and ventilation effectiveness in patient rooms: performance assessment using ventilation indices, ASHRAE Transactions: Symposia, MN-00-11-3. [61] Michaelson, G. S., Vesley, D., and Halbert, M. M., 1966, The laminar airflow concept for the care of low resistance hospital patients, Paper presented at the annual meeting of American Public health Association, Nielsen, P. V., 1989, Numerical prediction of air distribution in rooms, ASHRAE, Building systems: room air and air contaminant distribution, 1989. [62] Nielsen, P. V., 1989, Representation of boundary conditions at supply openings, IEA, Annex 20, Research item no. 1.11.