Mechanical Systems Thesis Proposal: Calvert Memorial Hospital Prince Frederick, MD Holly Mawritz

Transcription

1 : Holly Mawritz Senior Thesis Project Proposal Penn State University Department of Architectural Engineering Mechanical Emphasis Faculty Consultant: Dr. Jim Freihaut

2 Table of Contents: Executive Summary 2 Background: Existing Mechanical Systems 3 Air Systems 3 AHU-3 3 AHU-4 3,4 Water Systems 4 Heat Pumps 4 Heat Pump Cooling Tower 4 Chilled Water Plant 5 Boiler Plant 5 Areas of Focus for Better Design Solutions 6,7 Proposed Design Solutions 8 Removal of Patient Room Heat Pumps 8 The Desiccant Wheel 9,10 Ultraviolet Germicidal Irradiation 10,11 Design Solution Methods 12 Removal of Patient Room Heat Pumps 12 The Desiccant Wheel 12,13 Ultraviolet Germicidal Irradiation 13 Breadth Ideas 14 Project Methods 15 Preliminary Research Resources 16 Calendar Schedule of Tasks

3 Executive Summary: This report is based on the collaboration of previously written research papers in preparation for the redesign of the mechanical systems of in Prince Frederick, Maryland. This proposal will assimilate an analysis of the hospital s mechanical, electrical, and structural systems. This project will be finished and presented in the Penn State University Architectural Engineering Senior Thesis Presentations at the end of the spring 2005 semester. The existing mechanical system is explained in basic detail to represent the current operation of the equipment. The objectives to the mechanical design rely heavily on indoor air quality and infection control. These issues will increase the building s first costs, but eventually the benefits of the proposed systems in this report will eventually overshadow the first cost expenses. The use of UVGI (Ultraviolet Germicidal Irradiation) systems for infection control in critical spaces and exhaust ducts will decrease insurance costs over time. The addition of desiccant wheels to the system cooling configuration will result in a reduction of some of the mechanical equipment sizes, which will also lower mechanical equipment costs. Smaller mechanical equipment creates a reduction in energy used. All of these topics will be discussed in further detain in this proposal. The scope of this proposal is to fully explain the mechanical redesign and include areas of breadth topics such as the electrical and structural systems. The impact of these proposed ideas will be evaluated in this thesis study. Lastly, there will be an estimated schedule that gives an outline of the research processes for this proposal. This timeline will begin in December 2004 with the initial thesis proposal and end in April 2005 when the Architectural Engineering Senior Thesis Presentations will begin. 2

4 Background: Existing Mechanical Systems: contains a plethora of different mechanical systems. Due to the complexity and size of the hospital, the areas of focus will include the 2 nd 5 th floor patient towers. Below is a summary of the mechanical systems serving these areas of the hospital. Many of these systems will be replaced or renovated in the proposal section of this report. Air Systems: AHU-3 AHU-3 is a commercial grade, constant volume air handling unit which was originally installed in The air handling unit resides in the second floor mechanical penthouse. The areas served by this unit are the Intensive Care areas and Isolation rooms on the second and third floors. The unit utilizes a percentage of outside air and has a rating of 4000 cfm at 3.0 inches of static pressure. The unit is in poor condition and lacks final filters. Due to these unsatisfactory conditions, the hospital has begun planning for expansion of the areas served by this air handling unit. The new air handler, AHU-PT-1 will replace the original AHU-3 and will remain in the second floor mechanical room and serve the same areas including the expanded areas. The planned capacity for the new air handler will be approximately 50,000 cfm. AHU-4 AHU-4 is a commercial grade, constant volume air handling unit which was also installed in This unit is located in the second floor mechanical penthouse and currently serves the first, second, and third floor corridors. This unit utilizes a percent of outside air and is rated for 11,000 cfm at 3.5 inches of static pressure. This unit is also in poor condition, and is also lacking the appropriate final filters. The hospital renovation plans are to remove the existing AHU-4 and using the new AHU-PT-1 as the unit to serve the new second floor patient expansion and 3

5 existing second and third floor patient towers. In addition, AHU-PT-1 will serve the Post-Partum on the first floor that is currently supplied by heat pumps. Water Systems: Heat Pumps Water source heat pumps are used to serve numerous portions of the hospital but serve a majority of the rooms involved in the hospital patient tower (floors two through five). The patient tower s heat pump systems serve the second and third floor patient rooms and the entire fourth and fifth floors of the hospital. The heat pumps can either cool the air by rejecting heat or heat the air by collecting heat from the central condenser water loop. The heat pumps are of varying ages and capacities. Removing the heat pumps and replacing them with an all-air system configuration has been discussed, but currently no new designs have been developed. Heat Pump Cooling Tower Approximately one-third of is served by water source heat pumps. These heat pumps reject to two cooling towers: Cooling Tower No.1 and Cooling Tower No.4. Cooling Tower No.1 is a 378 ton forced-draft cooling tower was installed in Cooling Tower No.4 is an induced-draft cooling tower of unknown capacity. Cooling Tower No. 1 serves the basement, first, second, and third floor heat pumps while Cooling Tower No.4 serves the fourth and fifth floor heat pumps. Both of the cooling towers are in poor condition. For winter operation, Cooling Tower No. 4 utilizes an electric boiler and a plate and frame heat exchanger for adding required heat to the loop. Also, the louvers required for optimal winter operation of Cooling Tower No. 1 are missing. The hospital already has plans of removing these heat pumps, but not for another years. 4

6 Chilled Water Plant The existing chilled water plant consists of three electric centrifugal chillers. These chillers are located in the basement mechanical room. Chiller No. 1 has a rated capacity of 110 tons and was installed in Chiller No. 2 and Chiller No. 3 each have a rated capacity of 260 tons and were both installed in The chiller plant s total capacity is 630 tons. Chiller No.1 uses R-22 refrigerant while Chiller No. 2 and Chiller No. 3 use R-134A refrigerant. The chillers operate with an entering chilled water temperature of 55 o F and a leaving chilled water temperature of 45 o F. All of the chillers are in good condition. Boiler Plant The main boiler plant is located in the basement of the hospital. The plant contains two hot water boilers, each having a rated capacity of 5021 MBH. They are both forced-draft, gas-fired, fire tube type and are each equipped with a Cyclonetic burner. They were installed in 1996 are in excellent condition. 5

7 Areas of Focus for Better Design Solutions: The main emphasis of the mechanical redesign of is to achieve a more desirable performance of the mechanical systems based on the assignment requirements. The topics proposed in this redesign report in no way imply that the current mechanical, electrical, or structural systems of are dangerous or in error. One of the primary focuses of health care facilities are indoor air quality, and infection and disaster control. Through time, these issues have become more critically studied. Hospitals must follow important design parameters to ensure that the occupants are not exposed to any harmful contaminants in the air. A new air distribution system must be designed for the patient tower of Calvert Memorial Hospital in order to maintain a healthier living environment for the hospital occupants. The patient tower consists of the second, third, fourth, and fifth floors. The majority of the spaces on each floor consist of patient rooms that are all conditioned by water-source heat pumps. The heat pumps contain condensate drip pans that collect moisture condensing on the evaporator coil in the air conditioning system. These drip pans allow molds and other particles to grow, eventually exposing bacteria and mold spores to the breathable air. It is proposed that all of the hospital s heat pumps located in patient rooms be removed and replaced with all overhead air systems. The existing cooling towers serving the heat pumps are presently in poor shape. A new single cooling tower is suggested to replace the other cooling tower configuration. The cooling tower capacity will be further calculated once the heat pumps are removed and the new room loads are calculated. The Chilled Water and Boiler Plants, will most likely need replacements and modification due to the new system configurations. In continuing the quest for a healthier indoor air environment, humidity control must also be taken into consideration. Humid air creates the possibility for molds and bacteria to 6

8 grow, allowing infections to possibly spread from person to person. A drier air environment is needed; therefore a Desiccant Wheel will be implemented to air system. Along with the desiccant wheel configuration, UVGI (Ultraviolet Germicidal Irradiation) systems will be installed in the critical spaces and exhaust ducts. 7

9 Proposed Design Solutions: The following section describes a summary of the different design solutions to the mechanical systems being evaluated. In the solution for administering the proper indoor air quality and infection control of the hospital, the following ideas will be implemented to the building design: Removal of all patient room heat pumps, use of desiccant wheels in the building cooling system, and the installation of Ultraviolet Germicidal Irradiation in the critical care areas and exhaust ducts. Removal of Patient Room Heat Pumps The heat pumps serving the patient tower patient rooms contain bacteria and molds in the condensate drip pans. A drip pan is shaped to collect moisture condensing on an evaporator coil in an air conditioning of refrigeration system. Inadequate drainage of ductwork in terminal humidifiers can lead to potential downstream condensation, which may cause microbial growth in air distribution systems. These contaminants are emitted into the breathable air space, creating unsatisfactory breathable air quantities. To eliminate this problem, the heat pumps will all be removed and replaced with all overhead air systems. By removing the heat pumps the amount of equipment that needs to be maintained will be minimized and the system will become more versatile for future modifications. The overhead air system replacing the heat pumps will be a variable-air-volume configuration. There will be two air handling units provided to serve these spaces. The first of the two units, AHU-PT-1 (old AHU-3) is currently serving areas of the second and third floor spaces. The second and third floor patient rooms that were originally conditioned by the heat pumps will be added to the existing air handling unit, AHU-PT-1. As described in the Existing Mechanical Systems portion on the proposal, the AHU-PT-1 is located in the second floor mechanical room. The entire fourth and fifth floors will be served by a new air handling unit that will be located on fifth floor patient tower roof. 8

10 The Desiccant Wheel In the cooling system of the building, it is proposed that desiccant wheels are installed to help control the hospital s humidity levels. Dehumidification is the main focus of the desiccant cooling system. It reduces the building s latent load by removing excess moisture from the air. Moisture reduction stops or slows bacteria from growing or traveling through the air. The reduction of the latent load also decreases the size of the chiller. The air temperature of the sensible load will be dry but very hot, so sensible coolers such as rotary heat exchangers, evaporative coolers or coiling coils will be installed and sized accordingly. The desiccant used can either be solid or liquid. In this analysis a liquid lithium bromide spray solution will be used. The liquid desiccants work based-on the principle of chemical absorption of water vapor from the air to be conditioned. The humid air will pass through the lithium bromide solution spray becoming dehumidified. This occurs because the desiccant solution has a lower water vapor pressure than the air passing through it. Over time, the desiccant solution will become diluted due to the water extracted from the air, so it must be fed to a regenerator. The regenerator will then heat the lithium bromide, causing moisture to transfer to the desiccant. The heated desiccant is then sprayed into the air stream of the outdoor air and the moisture is released and exhausted to the outside. The regenerated desiccant is then cooled and reused. The benefits of using the lithium bromide solutions vary.. The performance of the solution depends on the air temperature. Lower temperature are desired, therefore it is best to run the solution through a chiller. Also, the lithium bromide kills bacteria on contact so the liquid desiccant has the ability to deliver biologically uncontaminated air to the surroundings. There are also no wet surfaces to promote bacterial growth, so this system is more beneficial than using cooling coils. If there were any doubts or worries about the spread of the lithium bromide solution to the surrounding breathable air, the UVGI (Ultraviolet Germicidal 9

11 Irradiation) in the exhaust ducts would kill off any of the proposed particles. These UVGI systems will be further discussed in the following section of this proposal. Ultraviolet Germicidal Irradiation One of the major aspects of contamination control is ventilation. In Calvert Memorial Hospital an alternative measure will be taken through the use of UVGI (Ultraviolet Germicidal Irradiation). Two kinds UVGI will be used to control contamination; one alternative will be Ultraviolet placed in the exhaust air stream and the other will be Ultraviolet lamp fixtures placed in the critical space areas. By adding these two UVGI systems, there will be a significant initial expense to the hospital. But the systems will create a savings on the hospital s insurance issues due to the enhanced infection control configurations. The system will reduce energy costs due to the decreased outdoor air intake. Determining the amount of equivalent air flow received after installation of the UV systems and the kill rate of UVGI to that which is realized by adding ventilation for proper contamination control must be evaluated. The added ventilation dilutes the contamination as if the bacteria have been killed. The equivalent air flow for the addition of UV is found by comparing the added ventilation to the actual kill rate from UV. Duct irradiation will be used in the exhaust air stream. The duct irradiation sterilizes the air which flows through a portion of the exhaust air stream. In order to maintain efficient kill results, duct sizes will need to be sized as large as possible without being too much of a burden on cost. The reason for the larger ducts is to slow down the velocity of the air moving through the UV killing zone. The longer the contaminant particles remain in the UV killing zone, the more particles will be killed. By slowing down the air velocity of the duct, more harmful particles will be killed. 10

12 Upper room irradiation will be implemented in the critical areas of the hospital such as the patient rooms, intensive care units, and operating rooms. The Upper Room Irradiation involves UVGI lamp fixtures that will be suspended or mounted on the room s ceiling or walls. The bottom portion of the light will be shielded to direct all radiation upward and prevent the lamps from coming in contact with the direct sight of the occupants. In analyzing the upper room irradiation procedure, the following factors will be considered: distance from the source, humidity levels, dust in the air, height of the ceiling, and the mixing factors occurring in the rooms. These different factors will determine the effectiveness of the upper room radiation. 11

13 Design Solution Methods: The following section describes a brief explanation of the different methods that will be used to redesign the mechanical systems being evaluated. The design solution methods will decipher the proper indoor air quality and infection control of the hospital. ASHRAE Standard 62 will be used in evaluating the clean air procedures. The following methods will be explained: Removal of all patient room heat pumps, the use of desiccant wheels in the building cooling system, and the installation of Ultraviolet Germicidal Irradiation in the critical care areas and exhaust ducts. Removal of Patient Room Heat Pumps The heat pumps will all be removed and replaced with overhead air systems. Loads will be calculated for the second, third, fourth, and fifth floor patient tower rooms by the HAP (Hourly Analysis Program) to determine the appropriate air distribution to each space. Once these airflows are determined, the air handling units can be chosen. The existing unit located in the second floor mechanical room (first floor roof) should be able to handle the additional load requirements for the second and third floor patient rooms. An appropriate air handling unit will then be selected for the fourth and fifth floors as well. The first and fifth floor roof structural systems will be evaluated to determine if the structures will withstand the weight of the new equipment. The Desiccant Wheel Dehumidification is the main focus of the desiccant cooling system. An analysis of the reduction of the latent load will be administered, thus changing the capacities of some of the mechanical equipment. Examples of the changed equipment are: heat exchangers, evaporative coolers, cooling coils, and the chiller. The loads determined from the HAP analysis will assist in determining a total loads for rooms in question. 12

14 The liquid lithium bromide spray that will be desiccant material of the cooling system will then be evaluated in terms of effectiveness, cost and other benefits of the spray solution. A detailed analysis explaining the desiccant wheel cooling system configuration will also be implemented into the report. From the HAP loads as well as the desired operating temperature of the desiccant fluid, a new chiller will be chosen. Ultraviolet Germicidal Irradiation By running a new load analysis on the hospital patient rooms, a new ventilation requirement will be established. Since contamination control is heavily related to ventilation in buildings, this will decipher the usages of UVI (Ultraviolet Germicidal Irradiation) that will be employed in the hospital. The two kinds UVGI will be used to control contamination; one alternative will be Ultraviolet placed in the exhaust air stream the other will be Ultraviolet fixtures placed in the critical space areas. The system ductwork, both supply and exhaust, will be sized from the load. The equivalent air flow for the addition of UV will be evaluated by comparing the added ventilation to the actual kill rate from UV and then setting up the proper equations. This will also affect the sizes of the ducts for the duct irradiation procedure because the larger the duct size, the slower the air flow. The slower the air flow is, the more time the lithium bromide spray has to collect harmful particles to be killed. Upper room irradiation will be implemented in the critical areas of the hospital such as the patient rooms, intensive care units, and operating rooms. Due to the UVGI lamps being wall or ceiling mounted in the rooms, there will be an intense analysis of distances from the lamp source to the room occupant. It is important that the radiation emitted from the UVGI lamps does not come in direct site with the occupants. Humidity levels, dust in the air, height of the ceiling, and the mixing factors occurring in the rooms will also be evaluated. 13

15 Breadth Ideas: The mechanical redesign of will impact the other building systems in the construction and operational aspects. The breadth areas under analysis for this proposal are: electrical and structural. The complicated mechanical redesign requires there to be advanced electrical changes to the hospital s electrical systems. New UVGI (Ultraviolet Germicidal Irradiation) lamps, also known as upper room radiation, will be installed in the existing patient rooms and critical areas to help increase the building indoor air quality. New electrical loads will be evaluated for each space thus changing the system feeders, panel boards, and over current protection devices. The structural system of the hospital will be evaluated at the first floor roof and at the fifth floor roof. The existing air handling unit located in the second floor mechanical room (on the first floor roof) is designated as AHU-PT-1. This portion of the first floor roof will be analyzed to determine if the new AHU-PT-1 load will affect the existing structural members. The second and new air handling unit being evaluated will be placed on the roof of the fifth floor of the building. Here, the framing member sizes will be analyzed and compared to the existing structure to determine if there is a necessary increase in load. 14

16 Project Methods: The research and modeling of the previously proposed design schemes will be accomplished by using various design tools. The redesign of will begin with the mechanical systems and continue on with the breadth topics; the electrical and structural systems. The first area of analysis will be the new hospital loads. By researching the patient room and intensive care treatment areas, important data will be accumulated for the load calculation process. Information on the types of equipment, square footages, and occupants will be acquired by contacting. Information may also be attained from Leach Wallace Associates, who have already done previous work on the hospital. Carrier s Hourly Analysis Program will them be used to model the proposed new ventilation and air systems. With these calculations, research from the UVGI duct systems and desiccant cooling configurations will be evaluated. After the mechanical depth has been established, the breadth work on the electrical system will begin. The electrical system will change due to the installation of UVGI lamps located in the critical patient areas. A lighting compliance will be administered using the ASHRAE Standard to ensure that the proper lighting is being delivered to each of the spaces. The 2002 National Electric Code will be utilized to make alterations to the electrical designs. The addition of air handling units and energy recovery equipment will prompt the structural analysis. The STAAD program will be used to determine if the loads of the new equipment meet the structure requirement. These results will be compared to the existing conditions and will be altered if needed. 15

17 Preliminary Research Resources: Bahnfleth, W. P., PhD, PE, W. J. Kowalkski,. PhD, PE. Airborne-Microbe Filtration in Indoor Environments. HPAC Engineering. Jan. 2002: pp Finkelstein, Hal. Contamination Control, Ventilation: A Guide to Engineering, Design, & Operations. Washington, D.C.: The National Resource Center, Hansen, Wayne, PE, REA, CEM. A Guide to Managing Indoor Air Quality in Health Care Organizations. Oakbrook Terrace: Joint Commissions on Accreditation of Healthcare Organizations, Memarzadeh, Farhad. Handbook on Assessing the Efficacy of Ultraviolet Germicidal Irradiation and Ventilation in Removing Mycobacterium Tuberculosis. Bethesda: National Institutes of Health, Natural Gas Desiccant Systems. Uniongas: A Duke Energy Company. Union Gas Limited Dec < Streifel, Andrew J., MPH, REHS. Health-Care IAQ: Guidance for Infection Control. HPAC Heating/Piping/Air-Conditioning Engineering. Oct. 2000: pp

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