2007 ashrae applications handbook

Dust collection must be known to determine the actual moisture load in the space. Makeup air must be preheated.

Equipment must be explosion-proof. Exhaust must be cleaned by filtration and solvents reclaimed or scrubbed. Volume manufacturers usually install a solvent Dressing room 72 to 74 40 to 50 recovery system for area exhaust systems. Filler tobacco casing and conditioning 75 75 Conversely, ideal storage conditions for color materials necessitate refrig- erated or deep-freeze temperatures to ensure quality and color balance when Filter tobacco storage and preparation 77 70 long storage times are anticipated.

All areas except finished film storage require a minimum of medium-efficiency particulate air filters. Moisture in vegetable and animal temperature over time is more important than the temperature materials and some minerals reaches equilibrium with moisture in level. Usually, conditions are selected for personnel comfort and the surrounding air by regain the percentage of absorbed moisture to prevent a film of moisture on the surface.

Tableting typically requires rium at various relative humidities. Sudden temperature changes Moisture Regain cause slight changes in regain even with fixed relative humidity, but Air temperature and relative humidity markedly influence pro- the major change occurs as a function of relative humidity.

Manufacturing economy precision machinery. Uniform relative humidity allows high- speed machinery to operate efficiently. Static Electricity Some materials may be exposed to the required humidity dur- Static electricity is often detrimental in processing light materi- ing manufacturing or processing, and others may be treated sepa- als such as textile fibers and paper, and extremely dangerous where rately after conditioning and drying.

Conditioning removes or potentially explosive atmospheres or materials are present. Static adds hygroscopic moisture. Drying removes both hygroscopic electric charges are generally minimized when relative humidity is moisture and free moisture in excess of that in equilibrium. Conditioning or drying is frequently a con- areas of low relative humidity. Such areas could be sources of static tinuous process in which the material is conveyed through a tunnel electricity.

The parts assembly area of an ammunition plant should and subjected to controlled atmospheric conditions. Systems and Equipment. In manufacturing metal products, temperature and relative hu- However, humidification is not a cure-all for static electricity midity must be kept sufficiently low to prevent hands from sweating, problems. Salt and acid in perspiration can cause corrosion and rust in resistivity. Examples include uncontaminated surfaces of some poly- a few hours.

Manufacture of polished surfaces and of steel-belted meric materials e. These surfaces can accumulate static prevent surface abrasion. Air Cleanliness 3. The Condensation can be prevented by eliminating thermal short cir- Occupational Safety and Health Administration OSHA sets stan- cuits, installing proper insulation, and using vapor barriers. Standards for safe levels of contaminants in the work environ- Personnel engaged in some industrial processes may be subject ment or in air exhausted from facilities do not cover everything to a wide range of activity levels for which a broad range of temper- that may be encountered.

Minimum safety standards and design atures and humidities are desirable. Department of Health agencies Handbook—Fundamentals addresses recommended indoor condi- such as the National Institute of Health, National Cancer Institute, tions for a variety of activity levels.

The U. Department of Energy and If layout and construction drawings are not available, a complete Nuclear Regulatory Commission establish standards for radioac- survey of existing premises and a checklist for proposed facilities tive substances. New industrial buildings are typically single story with a flat roof Thermal Control Levels and ample height to distribute air and utilities without interfering with Industrial plants are usually designed for an internal temperature process operations.

Tighter controls are often heights up to 12 ft, high-output fluorescent fixtures up to 20 ft, and dictated by the specific operations and processes located in the building. Single or multistory Handbook—Fundamentals for a more detailed analysis of work 2.

Type and location of doors, windows, crack lengths rate, air velocity, rest, and the effects of radiant heat. Structural design live loads Temperature control becomes tighter and more specific if person- 4. Floor construction nel comfort rather than avoidance of heat stress becomes the crite- 5. Exposed wall materials rion. Work- 7. Location of existing inlet and exhaust equipment 9. Building orientation temperature changes and can be cooled by increasing the air veloc- ity. Use of Building 1.

Product needs Contamination Control Levels 2. Surface cleanliness; acceptable airborne contamination level 3. Personnel needs, temperature levels, required activity levels, and plants and laboratories.

Gases and vapors are found near acid baths special workplace requirements and tanks holding process chemicals. Plating operations, spraying, 5. Floor area occupied by machines and materials mixing, abrasive cleaning, and other processes generate dust, 6. Clearance above floor required for material-handling equipment, fumes, and mists. Many animal and laboratory procedures e.

Air- 7. Unusual occurrences and their frequency, such as large cold or hot conditioning and ventilation systems must minimize exposure to masses of material moved indoors these materials. When airborne, these materials greatly expand their 8. Frequency and length of time doors open for loading or unloading range and potential for affecting more people. Chapter 11 of the 9. Machinery loads, such as electric motors size, diversity , large latent loads, or radiant loads from furnaces and ovens materials.

Potential for temperature stratification Concentrations of gaseous flammable substances must also be Design Conditions kept below explosive limits. Acceptable concentrations of these 1.

Wind velocity vides data on flammable limits and their means of control. Makeup air required Instruments are available to measure concentrations of common 5. Indoor temperature and allowable variance gases and vapors, but specific monitoring requirements and meth- 6. Indoor relative humidity and allowable variance ods must be developed for uncommon ones. Indoor air quality definition and allowable variance 8. Outdoor temperature occurrence frequencies 4. Operational periods: number per day and duration Waste heat availability and energy conservation incentives Required environmental conditions for equipment, process, Pressurization required and personnel comfort must be known before selecting HVAC Mass loads from the energy release of productive materials equipment.

The engineer and owner jointly establish design crite- Code and Insurance Requirements ria, including the space-by-space environment in facilities, pro- 1.

State and local code requirements for ventilation rates, etc. Occupational health and safety requirements recovery, load factors and equipment diversity, lighting, cleanli- 3. Insuring agency requirements ness, etc. Consider separating dirty processes from areas that Utilities Available and Required require progressively cleaner air. Gas, oil, compressed air pressure , electricity characteristics , steam Insulation should be evaluated for initial cost and operating and pressure , water pressure , wastewater, interior and site drainage energy cost savings.

When high levels of moisture are required in 2. Rate structures for each utility the building, the air-conditioning and structural envelope must 3.

Lighting Makeup Air design considers light quality, diffusion, room size, mounting height, Makeup air provides ventilation and building pressurization. It and economics. Illumination levels should conform to recommenda- must be filtered and conditioned to blend with return air and then tions of the Illuminating Engineering Society of North America.

The quantity of makeup air Air-conditioning systems can be located on the roof of the build- must exceed that of the exhaust air to positively pressurize the ing or ideally in an interior equipment room. Air intakes should building. Makeup air quantity may be varied to accommodate an not be located too close to loading docks or other sources of con- exhaust system with intermittently operating elements.

Heat and tamination. See the section on Air Filtration Systems. HVAC sys- cooling recovery from the exhaust airstream can substantially tem installation must be coordinated with other systems and reduce the outdoor air load.

A be required to reduce the quantity of health-threatening fumes, air- schedule of operations is helpful in determining heating and cooling borne bacteria, or radioactive particles.

Minimum ventilation rates loads. Economizers can take advantage of ambient conditions and 5. Heat is generated by fans that move and pressurize the air. This heat is not felt by the occupants but does add to the cooling load. Solar and Transmission The discharge air temperature of a draw-through cooling arrange- ment requires cooler air to the fan to accommodate the tempera- The roof load is usually the largest solar load on the envelope.

The increase is more Solar loads on walls are often insignificant, particularly because significant in systems with higher discharge air pressures. Insulating build- ing walls and roof almost always benefits HVAC cost and perfor- mance.

Because roof surfaces can become dirty, use a dark roof 6. Room-to-room pressurization is an essential method for contam- ination control. Without pressurization, surrounding contamination Internal Heat Generation e.

The cleanest room should quirements. Understanding equipment operating schedules allows have the highest room pressure, with decreasing pressure corre- an appropriate diversity factor to be applied to the actual power con- sponding to decreasing cleanliness. A differential pressure around sumption. Using connected loads may greatly oversize the system. Processes tend to operate continuously, but may be shut down on Pressurization calculations can be performed by using the pro- weekends or at night.

Using the research project RP White and Pahwa for further infor- charts in Spitler, calculate the building exfiltration at designated mation. The sum of exfiltration air volume plus the HVAC system design. Moisture condensation on cold surfaces exhaust rate or required outdoor air, whichever is greater is the must be managed when the latent load becomes very large.

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