INTRODUCTION:

Energy consumption by heating, ventilation, and air conditioning (HVAC) systems is substantial and continues to rise. In affluent nations, the construction sector accounts for 20–40% of total energy consumption ^1, Sometimes exceeding other significant sectors like transportation and industry. HVAC systems are the most energy-intensive in the construction industry, accounting for around 50% of overall consumption, or 10% to 20% of total energy used^2. Building services and HVAC (heating, ventilation, and air conditioning) systems account for over half of the energy used in buildings^3,4.

Building sustainability depends on HVAC systems operating at peak efficiency throughout the duration of the building lifetime. Building industry experts are fully aware of this and have worked hard to enhance lifespan performance. Building operating flaws, legal force, and commissioning advantages were the three factors that Djuric and Novakovic considered when accounting for the requirements of building commissioning⁵.

Energy consumption has significantly increased as a result of the rising reliance on HVAC systems in commercial, industrial, and residential settings, especially during the summer. The development of energy-efficient HVAC systems is crucial to safeguarding consumers against rising electricity bills and the environment against the damaging effects of greenhouse gas emissions brought on by the usage of energy-inefficient electrical equipment. Today's science and technological advancements happen swiftly. Energy-efficient HVAC systems can be achieved through a variety of techniques. Nonetheless, a thorough grasp of the comfort levels of buildings is required in order to design effective solutions. The main goal of thermal comfort is to make people feel comfortable in their thermal surroundings. The ASHRAE standard 55-2004 should be followed in the design and calculation of air conditioning systems to regulate the temperature environment in a way that also delivers an acceptable

Standard of air quality within a building⁶.

Fig No. 1 HVAC System

AIR HANDLING UNIT (AHU):

An air handling unit, or AHU for short, is made up of components assembled in sizable, easily accessible units shaped like boxes. These units, known as modules, include the necessary ventilation components to clean, cool, or replenish the air within a structure or set of premises.

They are often mounted on the roofs of buildings, and air is circulated through ducts to reach every room in the structure.

MAIN FUNCTIONS OF AHU:

The AHU does more than only ensure that the inside is properly ventilated with outside air. It also manages:

· The air purification filters will provide filtration and quality control over the air that enters the interior, with the air quality remaining clean based on how long the filters last.

· Adjustment of the air temperature, which controls how hot or cold the air conditioning system gets inside to provide the ideal thermal experience.

· Monitoring relative humidity to improve comfort levels indoors.

On the other hand, the areas where the AHU is designed to be used are those with limited natural ventilation, high volumes of people moving through them at once, and significant amounts of people accumulating in one area at once, such as conference halls, restaurants, and hotel dining rooms. It is also a good choice for areas that have strict hygienic standards, such clean rooms, operating rooms, and labs. Additionally, an AHU may be utilized to ventilate spaces that have underfloor heating or radiators for air conditioning^.7

Fig no. 2Air Handling Unit

What Does an AHU Consist:

· Air intake: air handling units collect air from outside, which is treated and distributed throughout the rooms; and/or indoor air that is "recycled".

· Filter: depending on the air purity requirements, the filter applied will have a higher or lower particle, viruses, bacteria, odours, and other air pollutants retention.

· Fan: this is an electromechanical system that powers the air to expel it from the AHU to the ducts that distribute the air throughout the rooms.

· Heat exchangers: devices that transfer temperature between two fluids, in this case, coolant and air, separated by a solid barrier.

· Cooling coil: the air passing through this module is cooled. In this process, water droplets can be generated, which are collected in a condensate tray thanks to the built-in droplet separator.

· Silencer: coatings that considerably reduce the sound level of the installation.

· Plenums: empty spaces in which the air flow is homogenised.

ACCEPTANCE CRITERIA:

Temperature: should be within 23°C ±2 and NMT 27°

Humidity: should be within 45±5% and NMT 55%

Heating and Cooling coils:

Depending on the locations and the application, air handling systems must provide heating, cooling, or both to alter the supply air temperature and humidity level. Heating and cooling coils in the air stream of the air handling unit offer this conditioning; the coils' actions are directly controlled by the medium that produces the heating or cooling effect. Usually, copper is used to make the coil's tubes, and aluminium or copper fins are added to help in heat transmission. Eliminator plates are also used by cooling coils to remove and discharge condensate water. A chiller provides chilled water, and a hot water generator produces hot waterTogether with the proper motorized control valve before the coil, downstream temperature sensors are usually utilized to monitor and regulate "off coil" temperatures. It is necessary to use a dehumidifier before using the cooling coil to overcool the area until the dew point is achieved and condensation forms. Air is reheated to the appropriate supply temperature using a heater coil that is positioned after the cooling coil. As a result, the supply air's relative humidity level decreases. Heating coils are frequently employed as the initial step of air treatment in colder areas where winter temperatures frequently fall below freezing, protecting chilled water coils or downstream filters from freezing. The management of the cold.^7,8

Ventilation-

The recommended amount of fresh air for various buildings is provided by ASHRAE standards. The requirement for cooling in a building is significantly increased by unconditioned air, which eventually raises the building’s HVAC systems’ total energy consumption. The highest limits of indoor air pollution concentrations, which are typically between 10% and 30% of the total air flow rate, are used to calculate the quantity of fresh air that is introduced into the central cooling plant⁹. Ventilation losses in contemporary structures can account for almost 50% of overall thermal losses¹⁰. Nonetheless, up to 50% of the electrical power utilized in residential structures may be accounted for by mechanical ventilation¹¹Additionally, mechanical ventilation systems account for between 20 and 40 percent of the energy used by air conditioning systems in hot and muggy areas¹². Compared to a typical air conditioner, the yearly energy consumption of an air conditioner with an enthalpy/membrane heat exchanger was studied¹³. They discovered that switching from a traditional HVAC system to a membrane heat exchanger can result in an annual energy savings of up to 8% in humid climates. Fernandez-Seara et al.'s experimental investigation of an air-to-air heat recovery unit with a sensible polymer plate heat exchanger for residential building ventilation systems was conducted. Fig. illustrates the configuration of their system with the heat recovery unit.¹⁴

Advantages:^15,16

· Rapid cooling: The air conditioning system can quickly reduce the interior temperature, giving users a convenient and pleasant atmosphere.

· Humidity control: In order to improve user comfort, it has the ability to manage both interior temperature and humidity.

· Air purification: To provide a cleaner interior atmosphere, it can both filter the air and eliminate indoor contaminants.

· Space saving: It doesn't need to take up any floor space because it can be mounted straight on the wall or ceiling.

· Uniform temperature: The HVAC system can provide uniform temperature for the whole room without localized areas of high or low temperature.

· Energy saving and environmental protection: Because HVAC systems utilize water or air to convey heat rather than a lot of power, they can be more ecologically friendly and energy efficient.

· Multiple energy sources: Many energy sources, including more ecologically friendly ones like solar and geothermal energy, can be used by the HVAC system.

Disadvantages:^17,18

· High energy consumption: Air conditioners have a high energy consumption since they need mechanical and electrical power to operate, and utilizing air conditioners will result in a significant rise in energy consumption.

· Harmful to health: Overuse of air conditioning can result in a marked drop in indoor air humidity, which can be detrimental to health and cause skin dryness.

· High cost: The installation of the air conditioning system is expensive and needs to be done by professionals. After that, the cost of maintenance might be substantial.- Minimal noise: It makes less noise and is quieter than the air conditioning system.

· High installation costs: The HVAC system require high costs to install, including equipment and labour costs.

· Difficult to maintain: It is complex and requires professional maintenance.

REFERENCES:

1. International Energy Agency. Online Energy Statistics, Energy Balances; 2008. http://www.iea.org/stats/

2. Pérez-Lombard L, Ortiz J, Pout C. A review on buildings energy consumption information. Energy Build. 2008; 40(3): 394–8.

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4. Annual energy outlook 2012 early release. Energy Information Administration (EIA). 2012

5. Djuric N, Novakovic V. Review of possibilities and necessities for building lifetime commissioning. Renew Sust Energy Rev. 2009;13(2): 486–92

6. ANSI/ASHRAE Standard 55–2004. Thermal Environmental Conditions for Human Occupancy, American Society of Heating Ventilating and Air Conditioning Engineers, Atlanta, GA, USA. 2004

7. HVAC design for pharmaceutical facilities; from Continuing education and development Inc.

8. HVAC system executes four canonic functions: Continuing education and development Inc. HVAC design for pharmaceutical facilities. 2008 ASHRAE handbook: heating, ventilating, and air.

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12. Zhang LZ. Progress on heat and moisture recovery with membranes: From fundamentals to engineering applications. Energy Convers Manage. 2012; 63: 173–95.

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15. Spitler JD. Ground-source heat pump researchpast, present and future. HVAC&R Res. 2005;11:165–7

16. United Nations Environment Programme. Buildings and climate change: summary for decision-makers, New York –USA. 2009

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Received on 16.04.2024 Modified on 06.06.2024

Asian J. Pharm. Ana. 2024; 14(3):191-194.

DOI: 10.52711/2231-5675.2024.00034