SYSTEM

WHAT IS YOUR SYSTEM TO ACHIEVE:
Before starting to design a system, it is critical that you what your system is to achieve.
Often ,the objective is to provide a comfortable environment for the human occupants, but there are many other possible objectives: creating a suitable environment for regulating a hospital operating room, maintaining cold temperatures for frozen food storage; or maintaining temperature and humidity to preserve wood and fiber works of art. Whatever the situation, and humidity is important that the object criteria for system success are clearly identified at the start of the project, because different requirements need different design considerations.
Let us very briefly consider some specific design situation and the types of performance requirements for HVAC system.
Example 1:hospital operating room. This is a critical environment , often served by a dedicated air conditioning system .the design objectives include:
1 ,heating to avoid the patient from becoming too cold.
2,coling to prevent the members of operating team from becoming too hot.
3, control adjustment by the operating team for temperatures between 65 F AND 80 F.
4, humidifying, to avoid low humidity and the possibility of static electricity sparks.
5, dehumidifying, to minimize any possibility of mold and to minimize operating team discomfort.
6, cleaning the incoming air with very high efficiency filter , to remove any airborne organisms that could infect the patient.
7, ventilation , to remove airborne contaminants and to keep the theatre fresh.
8, providing steady air movement from ceiling supply air outlets down over the patient for exhaust near the floor, to minimize contamination of the operating site.
This situation requires a very comprehensive air conditioning system.
Example 2:frozen food storage. The ideal temperature for long storage varies : i.e ice cream requires temperature below—12 F and meat requires temperature below –5 F . the design challenge is to ensure that the temperature is accurately maintained and that the temperature is an even as possible through out the storage facility. Her, accurate cooling and good air movement are the prime issuse. although cooling and air movement are required , we refer to this system as a “freezer” not as an air conditioning are not controlled.

AIR CONDITIONING PROCESSES

INTRODUCTION TO AIR-CONDITIONING PROCESSES:

As mentioned earlier, the term “air-conditioning”, when properly used , now means the total control of temperature, moisture, in the air (humidity), supply of outside air for ventilation, filtration of airborne particles , and air movement in the occupied spaces. There are seven main processes required to achieve full air conditioning and they explained below:

The processes are:

1-heating__ the process of adding thermal energy (heat) to the conditioned space for the purposes of raising puroses of raising or maintaining the temperature of the space.

2-cooling__the process of removing thermal energy (heat) from the conditioned space for the purposes of lowering or maintaining the moisture content of the air.

3-humidifying__the process of adding water vapor (moisture)to the air in the conditioned space for the purposes of raising maintaining the moisture the content of the air.

4-dehumidifying__the process fo removing water vapor (moisture) from the air in the conditioned space for the purpose of raising or maintaining the moisture content of the air.

5-cleaning__the process of removing particulates, (dust etc,) and biological contaminants, (insects, pollen etc,)from the air delivered to the conditioned space for the purposes of improving or maintaining the air quantity.

6-ventilation__the process of exchanging air between the outdoors and the conditioned space for the purpose of diluting the gaseous contaminants in the air improving or maintaining air quality, composition and fresh MECHANICAL VENTILATION. Natural ventilation is driven by natural by using fans to draw air in from outside or by fans that exhaust air from the spaces to outside.

7-air movement__the process of circulation and mixing air through conditioned spaces in the building for the purposes of achieving the proper ventilation and facilitating the thermal energy transfer.

MODREN HVAC

SCOPE OF MODERN HVAC:
Modern air conditioning is critical to almost every facet of advancing human activity. Although there have great advances in hvac, there are swveral areas where active research and debate continue.
Indoor air quality is one that directly affects us. In many countries of the world there is a rapid rise in asthmatics and increasing dissatisfaction with indoor-air –quality in buildings and planes.The causes and effects are extremely complex.A significant and engineering field has developed to investigate and address these issue.
Energy conservation is an ongoing challenge to find novel ways to reduce consumption in new and exiting building with out compromising comfort and indoor air quality. Energy requires significant cooperation between disciplines.
For example, electric lighting produces heat. When s system is in a cooling mode, this heat is an additional cooling load. conversely,when the system is In a heating mode, the lighting heat reduces the load on the building heating system. This interaction between lighting and HVAC is the reason that ASHRAE and the illumination engineering socity of north America (IESNA) joined forces to write the building energy convervation standard 90.1-2004, energy standard for building except low-rise residential buildings.
Greenhouse gas emissions and the destruction of the earth’s protective ozone layer are concerns that are stimulating research. New legislation and guidelines are evolving that encourage :recycling the use of new forms of energy;less energy usage;nad low polluting materials , particularly refrigerants. all these issues have a significant impact on building design, including HVAC system and the design codes

INTRODUCTION TO HVAC

OBJECTIVES:

The main processes of heating ,ventilation and air conditioning. There are no calculation to be done. The ideas will be addressed.

INTODUCTION:

Heating, ventilation and air conditioning, HVAC is a huge field. HVAC systems include a range from the simplest hand-stoked stove, used comfort heating to the extremely reliable total air-conditioning systems found domestic marines and space shuttles. Cooling equipment varies from the small domestic unit to refrigeration machines that are 10,000times the size, which are used in industrial processes.

Depending on the complexity of the requirements, the HVAC designer must consider many more issues than simply keeping temperatures comfortable. I will introduce you to the fundamental concepts that are used by designers to make decisions

About system design, operation, and maintenance.

HISTORY OF HVAC:

For millennia, people have used fire for heating. Initially, the air required to keep the fire going ensured adequate ventilation for the occupants. However as central furnaces with piped stream or hot water become available for heating the need for separate ventilation become apparent. By the late 1880s,rules of thumb for ventilation design were developed and used in many countries.

In 1851 Dr. john gorrie was granted U.S patent 8080for a refrigeration machine.By two main uses were freezing meat for transport and making ice. Howevre, in the early 1900s there was a new initiative to keep buildings cool for confort. cooling the NEW YORK STOCK EXCHANGE IN 1902 was one of the first comfort Comfort cooling system .comfort cooling was called “air-conditioning”.

SCOPE OF MODERN HVAC:

Modern air conditioning is critical to almost every facet of advancing human activity. Although there have great advances in hvac, there are swveral areas where active research and debate continue.

Indoor air quality is one that directly affects us. In many countries of the world there is a rapid rise in asthmatics and increasing dissatisfaction with indoor-air –quality in buildings and planes.The causes and effects are extremely complex.A significant and engineering field has developed to investigate and address these issue.

Energy conservation is an ongoing challenge to find novel ways to reduce consumption in new and exiting building with out compromising comfort and indoor air quality. Energy requires significant cooperation between disciplines.

For example, electric lighting produces heat. When s system is in a cooling mode, this heat is an additional cooling load. conversely,when the system is In a heating mode, the lighting heat reduces the load on the building heating system. This interaction between lighting and HVAC is the reason that ASHRAE and the illumination engineering socity of north America (IESNA) joined forces to write the building energy convervation standard 90.1-2004, energy standard for building except low-rise residential buildings.

Greenhouse gas emissions and the destruction of the earth’s protective ozone layer are concerns that are stimulating research. New legislation and guidelines are evolving that encourage :recycling the use of new forms of energy;less energy usage;nad low polluting materials , particularly refrigerants. all these issues have a significant impact on building design, including HVAC system and the design codes

FAN COIL UNITS

ASHRAE 2008