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Teaching Documents by Mir Aqueel Ali
Solar radiation measuring instruments
Electromagnetic radiation is a form of energy that propagates as both electrical and magnetic wav... more Electromagnetic radiation is a form of energy that propagates as both electrical and magnetic waves traveling in packets of energy called photons.
There is every possibility of formation of ice on the surface of the cooling coil, if the air is ... more There is every possibility of formation of ice on the surface of the cooling coil, if the air is used as source of heat either in primary circuit or in secondary circuit. This is because the moisture in the air will come out in the form of dew when the air is cooled in the cooling coil below both water freezing temperature and air dew point temperature, the frost will start to form. In other words, the frost starts to form when the contact happens between the cold surface of the heat exchanger (HX) and the near water vapor in the air due to the temperature difference. The colder the evaporator, the more water vapor will freeze out of the air. Hence the evaporator temperature must be as high as possible, while maintaining the desired room or fixture temperature. This means keeping a minimum or low-temperature difference (TD) between the entering air and the evaporator. A low TD is about 8 to 10°C. Four conditions help achieve a low TD: 1] a large evaporator surface, 2] a fully active evaporator, 3] a rapid circulation of air, 4] a clean, frost-free surface. These conditions for a given temperature promote slow frost buildup, high-suction pressure, high capacity, and efficiency. Less water vapor is removed from the air as frost. Humidity remains high. Foods lose less moisture and weight, and they keep their best appearance. Yet the Relative humidity (RH) also plays a major effect on the frost formation. Normally the frost growth rate is comparatively slow when RH is less than 40%. But when RH is high with high-temperature difference amid the cold surface and the surrounding air, the growth rate will appreciably increase. Initially, the influence of frost on the performance is negligible, but later the frost will start to accumulate more and more and reduce the micro-gap between fins and tubes. As a result, this will affect the whole system due to the partially airflow blockage or full blockage. Yet the contact resistance will reduce the heat transfer rate although the air-side heat transfer coefficient may increase moderately at the beginning stage. Notice that a further accumulation of the frost layers may jeopardize heat transfer performance and cause a much higher air-side pressure drop (ΔP) and increase the power consumption at the same time, and a typical power increase is in association with fan operation. Consequently, the coefficient of performance (COP) or the capacity of the refrigeration system will degrade appreciably and sometimes may even lead to system shutdown. The fan blades are also likely to be damaged if ice builds up on the fan ring. Frosting is unavoidable either in domestic refrigerator or in industrial installation.
Window air conditioner [WAC] is the most commonly used air conditioner for single rooms. In this ... more Window air conditioner [WAC] is the most commonly used air conditioner for single rooms. In this air conditioner all the components are enclosed in a single box. This unit is fitted in a slot made in the wall of the room, or more commonly a window sill. Plastic materials are receiving increased consideration in the design and fabrication of room air conditioners because of their ease in forming, inherent resistance to corrosion, and decorative qualities. Parts of the Window Air Conditioners WAC are one of the most widely used types of air conditioners because they are the simplest form of the air conditioning systems. WAC comprises of the rigid base on which all the parts of the WAC are assembled. The base is assembled inside the casing which is fitted into the wall or the window of the room in which the air conditioner is fitted. The whole assembly of the WAC can be divided into two compartments: the room side, which is also the cooling side and the outdoor side from where the heat absorbed by the room air is liberated to the atmosphere. The room side and outdoor side are separated from each other by an insulated partition enclosed inside the WAC assembly. The various parts of the WAC can be divided into following categories: the refrigeration system, air circulation system, ventilation system, control system, and the electrical protection system. SIZING AND PURCHASE OF WAC-One should go for cooling load calculation in order to arrive for appropriate sized AC. A large sized air conditioner penalizes in the following ways 1.It uses more energy. 2. It costs more to purchase than appropriate size AC. 3. The oversized AC cycles (on and off) more frequently reduce its efficiency. Frequent cycling makes indoor temperature to fluctuate more and results in less comfortable climate. It also inhibits dehumidification. It, in addition wears out the compressor and electrical parts more rapidly. Purchase energy five-star qualified WAC certified by India's bureau of energy efficiency BEE which consumes less energy. Its higher cost will be paid during its life span. Unless you have 3-4 hours usage of AC daily one can consider buying 3 or 5 stars non inverter AC. Purchase an AC with Energy saving features such as I) Digital readout for thermostat setting, ii) A built in timer, iii) A filter that slides out easily for regular cleaning iv) copper condenser. Air conditioners working on solar energy are available in market. The Refrigeration System of the Window Air Conditioner The refrigeration system of the WAC include the compressor, condenser, liquid line filter drier, expansion valve and the evaporator. The refrigerant used in most of the WAC was R22 [HCFC] which is now replaced by R410a [HFC binary blend of 50/50 by weight of HFC 32 and HFC 125], R32 and R290 [HC].
Domestic refrigerators and freezers are among the most energy demanding appliances in a househol... more Domestic refrigerators and freezers are among the most energy demanding appliances in a household due to their continuous operation. Worldwide the no. of consumers is constantly increasing. Refrigerators consume about ¼ th of the total energy consumption in a house. It also accounts to about 1/6 th of greenhouse gas emission. Although, the recent technologies use hydrocarbon as a refrigerant to reduce the greenhouse gas emission; the overall performance enhancement of domestic refrigerator is mandatory to reduce the indirect emissions and the amount of energy consumption. Most of the household refrigerator commonly used, works on vapor compression refrigeration cycle with cop around 1.7. However, some refrigerators use absorption systems, and, in some cases, thermoelectric (Peltier-effect) refrigeration with COP of 0.2 and 0.1 respectively. The refrigerant vapor is compressed by means of compressor to a pressure at which temperature obtained at the end of compression will be more than atmosphere, so that at this high temperature it will reject heat and will get condensed. This condensate is then allowed to pass through a capillary so that the pressure and temperature are lowered. Capillary device acts as throttle. A portion of the capillary tube is usually soldered to the suction line to form a heat exchanger. Whirlpool's insulated capillary technology surrounds the capillary with the super cold gas. Cooling refrigerant in the capillary tube with the suction gas increases capacity and efficiency. The discharge from evaporator will be either dry and saturated or super-heated, which then is sucked by compressor or cycle is completed. Along with above components there is liquid line filter drier [between condenser and capillary] and accumulator [between evaporator and compressor] so that the former will dry the refrigerant so as to remove moisture if at all present to avoid freezing in capillary. The later will not allow liquid refrigerant to pass to the compressor. Classification of Refrigerators-i. Depending upon usage Blood bank refrigerator-Used for storage of blood. [Temp. range 2 to 6 o c.] Mortuary Refrigerator-Used for Storage of dead bodies. [Temp. range 0 to 4 o c] House hold refrigerator-Used for storage of food items and in preparation of ice. Biological refrigerator-Used in hospitals, pharmacies, medical laboratories and serum preservation [ Temp. range 1 to 3 o c ]
Books by Mir Aqueel Ali
Low Medium High Minimum battery SOC [%] 80-90 40-60 30-50 Functions Start/Stop Reg. Braking Acces... more Low Medium High Minimum battery SOC [%] 80-90 40-60 30-50 Functions Start/Stop Reg. Braking Accessories powering Battery charging Start/Stop Reg. Braking Fill & boost Battery charging Start/Stop Reg. Braking Electric Traction Fill & boost Battery charging Battery chemistry Lead-acid Li ion/ Ni-MH Li-ion
Talks by Mir Aqueel Ali
Solar radiation measuring instruments
Electromagnetic radiation is a form of energy that propagates as both electrical and magnetic wav... more Electromagnetic radiation is a form of energy that propagates as both electrical and magnetic waves traveling in packets of energy called photons.
There is every possibility of formation of ice on the surface of the cooling coil, if the air is ... more There is every possibility of formation of ice on the surface of the cooling coil, if the air is used as source of heat either in primary circuit or in secondary circuit. This is because the moisture in the air will come out in the form of dew when the air is cooled in the cooling coil below both water freezing temperature and air dew point temperature, the frost will start to form. In other words, the frost starts to form when the contact happens between the cold surface of the heat exchanger (HX) and the near water vapor in the air due to the temperature difference. The colder the evaporator, the more water vapor will freeze out of the air. Hence the evaporator temperature must be as high as possible, while maintaining the desired room or fixture temperature. This means keeping a minimum or low-temperature difference (TD) between the entering air and the evaporator. A low TD is about 8 to 10°C. Four conditions help achieve a low TD: 1] a large evaporator surface, 2] a fully active evaporator, 3] a rapid circulation of air, 4] a clean, frost-free surface. These conditions for a given temperature promote slow frost buildup, high-suction pressure, high capacity, and efficiency. Less water vapor is removed from the air as frost. Humidity remains high. Foods lose less moisture and weight, and they keep their best appearance. Yet the Relative humidity (RH) also plays a major effect on the frost formation. Normally the frost growth rate is comparatively slow when RH is less than 40%. But when RH is high with high-temperature difference amid the cold surface and the surrounding air, the growth rate will appreciably increase. Initially, the influence of frost on the performance is negligible, but later the frost will start to accumulate more and more and reduce the micro-gap between fins and tubes. As a result, this will affect the whole system due to the partially airflow blockage or full blockage. Yet the contact resistance will reduce the heat transfer rate although the air-side heat transfer coefficient may increase moderately at the beginning stage. Notice that a further accumulation of the frost layers may jeopardize heat transfer performance and cause a much higher air-side pressure drop (ΔP) and increase the power consumption at the same time, and a typical power increase is in association with fan operation. Consequently, the coefficient of performance (COP) or the capacity of the refrigeration system will degrade appreciably and sometimes may even lead to system shutdown. The fan blades are also likely to be damaged if ice builds up on the fan ring. Frosting is unavoidable either in domestic refrigerator or in industrial installation.
Window air conditioner [WAC] is the most commonly used air conditioner for single rooms. In this ... more Window air conditioner [WAC] is the most commonly used air conditioner for single rooms. In this air conditioner all the components are enclosed in a single box. This unit is fitted in a slot made in the wall of the room, or more commonly a window sill. Plastic materials are receiving increased consideration in the design and fabrication of room air conditioners because of their ease in forming, inherent resistance to corrosion, and decorative qualities. Parts of the Window Air Conditioners WAC are one of the most widely used types of air conditioners because they are the simplest form of the air conditioning systems. WAC comprises of the rigid base on which all the parts of the WAC are assembled. The base is assembled inside the casing which is fitted into the wall or the window of the room in which the air conditioner is fitted. The whole assembly of the WAC can be divided into two compartments: the room side, which is also the cooling side and the outdoor side from where the heat absorbed by the room air is liberated to the atmosphere. The room side and outdoor side are separated from each other by an insulated partition enclosed inside the WAC assembly. The various parts of the WAC can be divided into following categories: the refrigeration system, air circulation system, ventilation system, control system, and the electrical protection system. SIZING AND PURCHASE OF WAC-One should go for cooling load calculation in order to arrive for appropriate sized AC. A large sized air conditioner penalizes in the following ways 1.It uses more energy. 2. It costs more to purchase than appropriate size AC. 3. The oversized AC cycles (on and off) more frequently reduce its efficiency. Frequent cycling makes indoor temperature to fluctuate more and results in less comfortable climate. It also inhibits dehumidification. It, in addition wears out the compressor and electrical parts more rapidly. Purchase energy five-star qualified WAC certified by India's bureau of energy efficiency BEE which consumes less energy. Its higher cost will be paid during its life span. Unless you have 3-4 hours usage of AC daily one can consider buying 3 or 5 stars non inverter AC. Purchase an AC with Energy saving features such as I) Digital readout for thermostat setting, ii) A built in timer, iii) A filter that slides out easily for regular cleaning iv) copper condenser. Air conditioners working on solar energy are available in market. The Refrigeration System of the Window Air Conditioner The refrigeration system of the WAC include the compressor, condenser, liquid line filter drier, expansion valve and the evaporator. The refrigerant used in most of the WAC was R22 [HCFC] which is now replaced by R410a [HFC binary blend of 50/50 by weight of HFC 32 and HFC 125], R32 and R290 [HC].
Domestic refrigerators and freezers are among the most energy demanding appliances in a househol... more Domestic refrigerators and freezers are among the most energy demanding appliances in a household due to their continuous operation. Worldwide the no. of consumers is constantly increasing. Refrigerators consume about ¼ th of the total energy consumption in a house. It also accounts to about 1/6 th of greenhouse gas emission. Although, the recent technologies use hydrocarbon as a refrigerant to reduce the greenhouse gas emission; the overall performance enhancement of domestic refrigerator is mandatory to reduce the indirect emissions and the amount of energy consumption. Most of the household refrigerator commonly used, works on vapor compression refrigeration cycle with cop around 1.7. However, some refrigerators use absorption systems, and, in some cases, thermoelectric (Peltier-effect) refrigeration with COP of 0.2 and 0.1 respectively. The refrigerant vapor is compressed by means of compressor to a pressure at which temperature obtained at the end of compression will be more than atmosphere, so that at this high temperature it will reject heat and will get condensed. This condensate is then allowed to pass through a capillary so that the pressure and temperature are lowered. Capillary device acts as throttle. A portion of the capillary tube is usually soldered to the suction line to form a heat exchanger. Whirlpool's insulated capillary technology surrounds the capillary with the super cold gas. Cooling refrigerant in the capillary tube with the suction gas increases capacity and efficiency. The discharge from evaporator will be either dry and saturated or super-heated, which then is sucked by compressor or cycle is completed. Along with above components there is liquid line filter drier [between condenser and capillary] and accumulator [between evaporator and compressor] so that the former will dry the refrigerant so as to remove moisture if at all present to avoid freezing in capillary. The later will not allow liquid refrigerant to pass to the compressor. Classification of Refrigerators-i. Depending upon usage Blood bank refrigerator-Used for storage of blood. [Temp. range 2 to 6 o c.] Mortuary Refrigerator-Used for Storage of dead bodies. [Temp. range 0 to 4 o c] House hold refrigerator-Used for storage of food items and in preparation of ice. Biological refrigerator-Used in hospitals, pharmacies, medical laboratories and serum preservation [ Temp. range 1 to 3 o c ]
Low Medium High Minimum battery SOC [%] 80-90 40-60 30-50 Functions Start/Stop Reg. Braking Acces... more Low Medium High Minimum battery SOC [%] 80-90 40-60 30-50 Functions Start/Stop Reg. Braking Accessories powering Battery charging Start/Stop Reg. Braking Fill & boost Battery charging Start/Stop Reg. Braking Electric Traction Fill & boost Battery charging Battery chemistry Lead-acid Li ion/ Ni-MH Li-ion