Air-conditioning methods

Example 28.1 All air A space is to he held at 21°C dry hulh and 50% saturation, and has an internal load of 14 kW sensible and 1.5 kW latent heat gain. The inlet grille system is suitable for an inlet air temperature of 12°C. What are the inlet air conditions and the mass air flow  

Inlet air temperature = 12.0°C Air temperature rise through room, 21 - 12 = 9.0 K 

Moisture content of entering air = 0.007 454 From tables [4], this gives about 85% saturation. 

Example 28.2 Chilled water For the same duty, a chilled water fan coil unit is fitted within the space. Water enters at 5°C and leaves at 10.5°C. The fan motor takes 0.9 kW. What water flow is required  

Example 28.3 Refrigerant For the same duty, liquid R.22 enters the expansion valve at 33°C, evaporates at 5°C, and leaves the cooler at 9°C. Fan power is 0.9 kW. What mass flow of refrigerant is required  

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These case examples illustrate the dependence of the stratification of temperature and contaminants on several parameters, which in some cases increase and in other cases decrease the effectiveness. Al the parameters should be included in calculations when designing the system combination of the room air conditioning methods. 

Many components of ships and marine stmctures are now coated in the shop under controlled conditions to reduce the amount of solvents released into the atmosphere, improve the quaUty of work, and reduce cost. Regulations designed to limit the release of volatile organic compounds into the air confine methods of shop apphcation to those having transfer efficiencies of 65%. Transfer efficiency is defined as the percent of the mass or volume of sohd coating that is actually deposited on the item being coated, and is calculated as... 

In industrial air-conditioning systems, harmful environmental gases, vapors, dusts, and fumes are often encountered. These contaminants can be controlled by exhaust systems at the source, by dilution ventilation, or by a combination of the two methods. When exhaust... 

FIG. 11-71 Methods of transforming low-pressure vapor into high-pressure vapor in refrigeration systems (Stoecker, Refrigeration and Air Conditioning). 

This chapter describes the room air conditioning process, including the interaction of different flow elements room air distribution, heating and cooling methods, process sources, and disturbances. Air handling equipment, including toom air heaters, is discussed in the form of black boxes as far as possible. 

Note Air distribution systems are not ventilation or air conditioning systems. For example, mixing air distribution and displacement air distribution are methods to bring the supply air to the treated space. 

A detailed description of the methods for room air conditioning is presented in Chapter 8. Table 2.1 summarizes the strategies. 

The main purpose for the heating and air conditioning of work spaces is to provide an environment that is acceptable and does not impair the health and performance of the occupants. During production processes and in the external environment it may be necessary to work in unacceptable conditions for a limited time period. However, it must be ensured that these conditions do not impair the health of the employees. Light, noise, air quality, and the thermal environment are all factors that influence the acceptability of conditions for and performance of the occupants. This section will only deal with the thermal environment. Several standards dealing with methods for the evaluation of the thermal environment have been published by international standard organizations such as ISO and CEN. 

Zonal models can be applied for each room air conditioning strategy (see Section 8.6), but they are mostly used in stratification and zoning strategies with different air distribution methods (see Section 8.7). 

A clear classification of the ideal strategies will help the evaluation of the present room air distribution methods in different operating conditions. It also creates a solid base for the development and promotion of new innovations in the field. 

Srratification is a desirable strategy to provide efficient room air condi-noning with much less effort than using the piston strategy. Its mam application in room air conditioning is the thermal replacement method. However, it can also be applied for contaminants without any thermal buoyancy sources that have different density from the room air. Examples of different air distribution methods to create thetma teplacement are presented in Fig. 8.12. 

However, the use of other room air distribution methods together with certain exhaust, heating, and cooling methods will also lead (intentionally or unintentionally) to the application of the mixing air conditioning strategy. Some examples are shown in Fig. 8.15. 

To conclude the example A different air conditioning strategy can and sometimes should be selected for different seasons or operating conditions. The strategy can be changed by using combinations of available method.s. 

The clarification of the room air conditioning strategies and their separation frtim the practical methods at present creates space for creativity and new innovations and their evaluation. 

These are used in conjunction with a ventilation or air-conditioning system and may be included in one of the following methods of ventilation. 

Air-conditioning systems make use of this method, as the cooler, dense air supplied from high level will drop to low level, picking up the space heat gains before extraction at low level. 

ASHRAE 110-1995. Method of Testing Laboratory Fume Hoods. Atlanta.. American Society of Heating, Refrigeration, and Air-conditioning Engineers, 1995. 

Clean air and many air contaminants are under normal conditions invisible. It is, however, often desired to actually see the movement of air or the emission and transport of contaminants in order to ensure good air quality.. Methods aimed at the visualization of airflow, contaminants emission to the air, and their transportation out in the workplace and to the breathing zone of the worker are therefore important tools for designers of industrial ventilation systems. 

The simplest way to calibrate a hygrometer is to use ambient air. The humidity of ambient air is measured using both the calibrated meter and the reference meter. A simple psychrometer or an Assmann hygrometer can be used as a reference. Provided the air conditions are stable, this method is used to check hygrometers in field measurements and other not too demanding purposes. 

ASHRAE 41.2-1987. Methods for Laboratory Air Flow Measurement. American Societv of Heating, Refrigerating, and Air-conditioning Engineers, Atlanta, 1987. 

A system is an ordered set of ideas, principles, and theories or a chain of operations that produces specific results to be a chain of operations, the operations need to work together in a regular relationship. A quality system is not a random collection of procedures (which many quality systems are) and therefore quality systems, like air conditioning systems, need to be designed. All the components need to fit together, the inputs and outputs need to be connected, sensors need to feed information to processes which cause changes in performance and all parts need to work together to achieve a common purpose i.e. to ensure that products conform to specified requirements. You may in fact already have a kind of quality system in place. You may have rules and methods which your staff follow in order to ensure product conforms to customer requirements, but they may not be documented. Even if some are documented, unless they reflect a chain of operations that produces consistent results, they cannot be considered to be a system. 

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