THERMODYNAMICS AND HEAT TRANSFER .pptx

Heat transfer and thermodynamics are two complementary branches of science. Thermodynamics deals with equilibrium states by outlining the relationship between energy and work, while heat transfer describes the physical mechanism to understand the transport of energy. Heat transfer paints a complete picture of the thermodynamic processes. In this lesson, we will explore the relationship between heat transfer and thermodynamics. We will recall the famous laws of thermodynamics and recap the energy equation.

1. KIT - KALAIGNARKARUNANIDHI INSTITUTE OF TECHNOLOGY B E AGRICULTURE ENGINEERING AIR FILTER LECTURE BY DR P BALAKRISHNAN ASSISTANT PROFESSOR THERMODYNAMICS AND HEAT TRANSFER SUBJECT

2. What is an overview of air filters? Air filters are essential devices designed to remove airborne contaminants, including particles, pollutants, and microorganisms, which can pose health risks and harm the environment. In manufacturing settings, they help maintain product and material quality, protect critical equipment, and prevent product loss. Cleanrooms use a combination of high efficiency particulate air (HEPA) filters, which are approximately 100 times more efficient than a typical furnace filter, with methods for controlling air flow to keep particulate counts within acceptable parameters. Exhaust and stack gasses are filtered and cleaned before releasing them into the atmosphere. Air filters are used in home furnaces, offices, laboratories, clinics, hi-tech microelectronics manufacturing, chip and hard-drive production and the aerospace industry.

3. How Do Air Filters Work? Air filters operate by drawing in contaminated air through their filter medium, which contains fine openings. Particles larger than these openings are captured and retained within the filter, effectively removing them from the air stream. As a result, the air exiting the filter has a significantly lower concentration of particles. Over time, the filtration efficiency improves as the buildup of particles on the filter’s upstream side helps trap additional contaminants. To maintain optimal performance and prevent airflow restriction due to clogging or blinding, the filter medium needs to be replaced or cleaned regularly.

4. What are the Efficiency of Air Filters? The Minimum Efficiency Reporting Value (MERV) is a scale used to assess how effectively air filters capture particles ranging from 0.3 to 10 microns in diameter. This rating helps determine the filter’s ability to maintain good air quality and allows for performance comparisons between different air filters. The MERV rating system was developed by the American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE). A higher MERV rating indicates a greater ability of the air filter to trap smaller particles. As the rating increases, the filter can capture finer particles. However, filters with higher MERV ratings often have a denser filter medium, which can reduce airflow, lead to higher energy consumption, and put additional strain on the HVAC system and its components.

5. Summary Air filters are devices used to remove airborne particles and pollutants that are hazardous to health and the ecosystem. These devices utilize a filter media, which captures those particles on its upstream side. Pleated air filters have folds or pleats, which increase their surface area. Non-pleated air filters provide maximum airflow and are suitable for higher airflow pressures. Air filter media can be made from paper, foam, carbon, aluminum, steel, fiberglass, or plastic. The performance of air filters is reported by the MERV rating, arrestance, dust holding capacity, dust spot efficiency, and MPPS. The MERV rating is commonly used; it refers to the air filter's efficacy in removing particles with sizes between 0.3 and 10 microns. HEPA filters capture at least 99.97% of particulates in the air measuring 0.3 microns in diameter. In ISO and European standards, the efficiency must be at least 99.95%. Impaction, interception, and diffusion are the filtration mechanisms that occur in HEPA filters.

6. ULPA filters remove particles of up to 0.12 microns in diameter for at least 99.99% efficiency. Their filter media density is higher than HEPA filters; hence, airflow is more restricted. Ionizer air filters and washable electrostatic air filters attract particulates by static electricity. Activated carbon filters and UV air filters remove toxic gases and microorganisms in the air respectively. HVAC air filters protect the critical components of the HVAC unit and purify the air for the users. The types of HVAC air filters are AC filters and furnace filters. Air filters used in vehicles are the engine air filters, cabin air filters, car exhaust filters, and diesel particulate filters (DPF). Baghouse filters are pollution control equipment that removes particulates and pollutants in flue gases from process equipment before releasing them into the atmosphere. Exhaust hood filters and exhaust filters are used in commercial and residential ventilation systems.