Fluidized-Bed Heat Exchangers! By Imran

Fluidized-Bed Heat Exchangers.

In a fluidized-bed heat exchanger, one side of a two-fluid exchanger is immersed in a bed of finely divided solid material, such as a tube bundle immersed in a bed of sand or coal particles, as shown in Fig. 1.3. If the upward fluid velocity on the bed side is low, the solid particles will remain fixed in position in the bed and the fluid will flow through the interstices of the bed. If the upward fluid velocity is high, the solid particles will be carried away with the fluid. At a ‘‘proper’’ value of the fluid velocity, the upward drag force is slightly higher than the weight of the bed particles. As a result, the solid particles will float with an increase in bed volume, and the bed behaves as a liquid. This characteristic of the bed is referred to as a fluidized condition. Under this condition, the fluid pressure drop through the bed remains almost constant, independent of the flow rate, and a strong mixing of the solid particles occurs. This results in a uniform temperature for the total bed (gas and par- ticles) with an apparent thermal conductivity of the solid particles as infinity. Very high heat transfer coefficients are achieved on the fluidized side compared to particle-free or dilute-phase particle gas flows. Chemical reaction is common on the fluidized side in many process applications, and combustion takes place in coal combustion fluidized beds. The common applications of the fluidized-bed heat exchanger are drying, mixing, adsorption, reactor engineering, coal combustion, and waste heat recovery

Physical Properties of Refrigerants R-417A Environmental Classification HFC! By Imran

Physical Properties of Refrigerants R-417A Environmental Classification HFC

Molecular Weight 106.8 Bubble Point (1 atm, ºC) -39.1 Critical Pressure (bar-abs) 40.4 Critical Temperature (ºC) 87.1 Critical Density (Kg/m^3) 520.6 Liquid Density (25 ºC, Kg/m^3) 1151.3 Vapor Density (bp,Kg/m^3) 5.681 Heat of Vaporization (bp, KJ/Kg) 200.75 Ozone Depletion Potential (CFC 11 = 1.0) 0 Global Warming Potential (CO2 = 1.0) 1950 ASHRAE Standard 34 Safety Rating A1 Temperature Glide (ºC) 5.5 Composition: A blend of HFC refrigerants R-125, R-134A and hydrocarbon R-600 (butane) (46.6 / 50 / 3.4 wt%) Application: An alternative to R-22 in medium temperature refrigeration and air conditioning. Performance: Both suction and discharge pressures will run lower than R-22, which may affect valve operation or orifice tube selection. Loss of capacity may be significant at lower evaporator temperatures, but generally not a problem in properly sized equipment at warmer application temperatures. Lubricant: The hydrocarbon component in R-417A helps promote oil return in systems containing mineral oil or alkylbenzene. Although HFC refrigerants won’t mix with these oils, the hydrocarbon addition thins the oil and keeps it moving around the loop. More complicated piping arrangements or large hold-up volumes may still require some oil be changed to POE. R-417A R-417A Available in the following sizes: 26R417ART 12 Kg RETURNABLE CYLINDER 44R417ART 20 Kg RETURNABLE CYLINDER 100R417ART 46 Kg RETURNABLE CYLINDER 1587R417ART 720 Kg RETURNABLE DRUM

Daikin ENVi Thermostat Installation Manual Step! By Imran

Daikin ENVi Thermostat Installation ManualStep

. Position and Wire the DPCA The Daikin Power and Communication Adapter (DPCA) provides an interface between the thermostat and Indoor Unit. To install the DPCA: 1. Position the DPCA in a suitable location, away from water and near the Indoor Unit (for example, a backside cavity of a wall-mounted unit). The DPCA is not plenum rated and should be mounted in a non-plenum space. 2. Connect the DPCA power cable to the Indoor Unit power supply terminals. Ensure that the electrical connections are securely tightened. 3. Remove the DPCA cover by grasping both sides and pulling along the length of the DPCA. 4. Use the Wiring Harness to connect the P2 terminal on the DPCA to the S21 terminal on the Indoor Unit’s main PCB. Refer to the Daikin system installation manual for information about accessing the S21

Step 3. Install the Daikin ENVi Thermostat The ideal location for the thermostat is approximately 5 ft (1.5 m) above floor level in the main living area. Do not install the thermostat: Close to sources of heat such as incandescent lights Near supply heating/cooling sources In direct sunlight On exterior, non-insulated or poorly insulated walls In the kitchen or other areas of potentially high heat and/or humidity In an area that could restrict air flow To install the thermostat:

1. If necessary, remove the previous thermostat. 1. Gently separate the backplate from the Daikin ENVi thermostat. 2. Place the thermostat backplate on the wall. Make sure that any existing wires can be inserted through the opening for the wiring. If the backplate does not adequately cover the area where the previous thermostat was installed, attach the trim plate to the back of the backplate to increase its coverage. 3. Using the backplate as a template, mark the location of the

AHU PRE-FILTER FUNCTIONS! By Imran

PRE-FILTER FUNCTIONS

Pre-filters are a nice feature to have in your air purifier. It also expands the lifetime of HEPA and activated carbon filters which follow after pre-filter. The pre-filter is the front line in an air purifier, and it captures largest particles which the primary filter usually can’t do. Pre-filters come as a very handy feature that strengthens air filtering technology by preventing debris getting into the next, primary filter. Pre-filters usually have a long lifetime because they can be washed, vacuumed and replaced whenever it`s necessary. If your air purifier is running all the time, then it`s recommended to clean the pre-filter at least one a month. Otherwise, pollution such as fur, pollen, dust and hair will get stucked in the pre-filter after a while, and it will dramatically decrease the overall performance of an air purifier. Washable filter is a great plus, which will save you a lot of money long term

Eventually, after a longer period, the pre-filter will wear out, after many times of cleaning it, and active air-purifying day after day. So, if you want to keep it safe then buy a new pre-filter and change the old one, when you feel that it is necessary.

Screw compressor! By Imran

Screw compressor By Imran

How does a screw compressor work? Here we will look a bit closer at the screw air compressor technology. What is a screw compressor and what is its basic working principle? The screw element was first developed in 1930s, it has a male and female rotors, the male rotor drives the female rotor if it’s an oil injected screw compressor technology; and a timing gear drive both rotors in the oil free compressor technology as both rotors will run harmonically with minimum calculated clearance between both elements. The basic principle of a screw compressor is as the male and female rotors are rotating in opposite direction they draw air in between them. As the air progresses along the rotors the air is compressed as the volume space between the rotors decreases, hence creating compressed air that is displace to the outlet. The speed of the rotors is optimised at a certain level to minimise mechanical loses (due to heat at very high speed) and volumetric losses (air losses due to very low speed). Unlike a piston compressor a screw compressor generally doesn’t have valves and has no mechanical force that causes unbalance, this means that it can work at a high speed combined with large flow rates and still be contained within a small exterior. A good example of a screw compressor that can produce large volumes of compressed air and with a small footprint is Atlas Copco’s

Scroll Compressor! By Imran

SCROLL COMPRESSOR A scroll compressor is a specially designed compressor that works in a circular motion, as opposed to up-and-down piston action.

Scroll compressors are becoming more popular for use in HVAC systems, as they are more reliable and efficient than reciprocating types. A scroll compressor has one fixed scroll which remains stationary and another moving or orbiting scroll that rotates through the use of a swing link. When this happens, the pockets of refrigerant between the two scrolls are slowly pushed to the center of the two scrolls, causing the reduction of the volume of the gas. It is then discharged though the center port to the condenser. The advantage of a scroll compressor is that it has fewer moving parts and less torque variation compared to the reciprocating compressor. This advantage is translated to a smooth and quiet operation. The scroll compressor is also known as scroll pump or scroll vacuum pump. Scroll compressors can be applied in several different ways to meet a homeowner’s needs for efficiency, comfort, and affordability. Single-stage compressors are found in most home cooling and heating systems. The simplest and least expensive type, they operate at only one speed. Single-stage units can cool or heat a home efficiently. Two-stage compressors operate at two different speeds, more closely matching their cooling or heating output to the exact needs of the home. The ability to run at a lower, more efficient speed helps remove excess humidity from the air while saving energy and the compressor can switch to its full capacity if needed to hold temperatures steady. Two-stage systems are typically more energy-efficient than single-stage systems

CALCULATING RELATIVE HUMIDITY ! By Imran

CALCULATING RELATIVE HUMIDITY By Mohammad Imran

Calculating the RH requires the correct equation(s). The RH is the amount of moisture in the air (via moisture mass or vapor pressure) divided by the maximum amount of moisture that could exist in the air at a specific temperature (via max moisture mass or saturation vapor pressure). RH is expressed as a percentage and has no units since the units in both the numerator and denominator are the same. The percentage is found by multiplying the ratio by 100%. The RH is NOT the dewpoint divided by the temperature. For example, if the temperature was 60 F and the dewpoint was 30 F, you would not simply take (30/60)*100% = 50% RH. Method #1 When given temperature and dewpoint, the vapor pressure (plugging Td in place of T into Clausius-Clapeyron equation) and the saturation vapor pressure (plugging T into Clausius-Clapeyron equation) can be determined. The RH = E/Es*100%. Clausius-Clapeyron equation LN(Es/6.11) = (L/Rv )(1/273 - 1/T) Es = Saturation vapor pressure L = Latent heat of vaporization = 2.453 × 10^6 J/kg Rv = Gas constant for moist air = 461 J/kg T = Temperature in Kelvins Method #2 The mixing ratio is defined as the mass of water vapor divided by the mass of dry air. In a lab setting, the lab technician could measure both the mass of water vapor and mass of dry air in an air sample. The mass of water vapor in a sample of air divided by the mass of dry air is W. The lab technician could then saturated the air (making sure temperature remains the same) and recalculate the mass of water vapor divided by the mass of dry air. This would be Ws. The RH = W/Ws*100% To get W and Ws, use the equation: W= (0.622*e) / (P - e) and Ws = (0.622*Es) / (P - Es) This requires that E and Es are known. Therefore, without using the Clausius-Clapeyron equation, calculating RH outside of a lab setting is difficult. --operational methods of calculating RH-- 1. Mixing ratio can be determined using the Skew-T log-P diagram. For any pressure level, the mixing ratio is read through the dewpoint and the saturation mixing ratio is read through the temperature. By reading the mixing ratio values off the Skew-T you can determine W and Ws for any temperature and dewpoint. RH = W/Ws*100% 2. Take the temperature and dewpoint and plug them into the Clausius-Clapeyron equation. There are computer programs that will do this. The computer uses the graph of the Clausius-Clapeyron equation for all temperature and dewpoints to find RH. 3. Many textbooks have a graph or table data of saturation mixing ratio and/or saturation vapor pressure for various temperatures. Using dewpoint will either give the actual vapor pressure or actual mixing ratio while using temperature will either give the saturation vapor pressure and saturation mixing ratio (depending on if graph is showing vapor pressure or mixing ratio). RH is E/Es*100% or W/Ws*100%.

Symptoms of brain fever 90 plus child death in Bihar due to brain fever

Symptoms of brain fever:

1. Pain in the heart 2. Feeling weak in the muscles 3. Haemiparesis - Feeling weakness in all outer organs of the body, nausea or vomiting 4. Gradient, back and shoulder stiffness 5. On cerebral fever The person also changes in mental condition as well as a high fever and cold. Due to brain fever: 1. In a cerebral fever, people are suffering from brain fever like various viruses such as Rabbis virus, Herpes simplex polio virus, measles virus, and smallpox virus. Also Read - International Yoga Day 2019: PM Modi told, how to learn the benefits of Shalabhasan, how to know 2. Some people have swelling in the brain when a fever is fever. And this swelling occurs from the infection of any lethal virus. Fatal viruses such as Japanese encephalitis virus, St. Lucie Virus, West Nile virus, etc. are the major causes of viral encephalitis 3. Bacterial encephalitis is caused by a very fatal infection. Encephalitis is mainly of two types of primary encephalitis and secondary encephalitis

134A pressure chat! by Imran

410A Pressure Chart ! By Imran

Failure causes of thermostatic expansion valve TXV ! By Imran

thermostatic expansion valve or TXV — can cause a number of symptoms in a system. Here are the ways a TXV can become restricted:

Wax buildup in the valve because the wrong oil was used in the system; Sludge from the byproducts of a compressor burnout; Partial TXV orifice freeze-up from excessive moisture in the system; Foreign material in the orifice; Oil-logged TXV from refrigerant flooding the compressor; Too much oil in the system; TXV is adjusted too far closed; Manufacturer’s defect in the valve; or Plugged inlet screen on TXV https://www.youtube.com/channel/UCej-mX5F6GqsPlhhHrQC4Nw

Cause and Troubleshooting an Overheating Compressor ! By Imran

Troubleshooting an Overheating Compressor

Here are a few tips you can try to find the issue before contacting a professional: High head pressure can be caused by dirty condenser coils, a faulty condenser fan, too much refrigerant or perhaps some other heat source near the compressor such as a dryer vent. An electrical problem outside of the A/C also may cause a compressor to overheat, such as voltage issues or spikes in power. This may be a problem with your home's electrical system or something external such as electrical transformer or grid issues. An issue called "high superheat" can be caused by not enough refrigerant in the system, a kink or restriction in the refrigerant line, a malfunctioning metering component or a hot-liquid line too close to the compressor, such as a hot-water pipe. If the compressor is short-cycling, this also can cause overheating. The problem might be due to a dirty air filter or evaporator coil, or a faulty capacitor or metering device

SCROLL COMPRESSOR ! By Imran

A scroll compressor is a specially designed compressor that works in a circular motion, as opposed to up-and-down piston action.

Scroll compressors are becoming more popular for use in HVAC systems, as they are more reliable and efficient than reciprocating types. A scroll compressor has one fixed scroll which remains stationary and another moving or orbiting scroll that rotates through the use of a swing link. When this happens, the pockets of refrigerant between the two scrolls are slowly pushed to the center of the two scrolls, causing the reduction of the volume of the gas. It is then discharged though the center port to the condenser. The advantage of a scroll compressor is that it has fewer moving parts and less torque variation compared to the reciprocating compressor. This advantage is translated to a smooth and quiet operation. The scroll compressor is also known as scroll pump or scroll vacuum pump. Scroll compressors can be applied in several different ways to meet a homeowner’s needs for efficiency, comfort, and affordability. Single-stage compressors are found in most home cooling and heating systems. The simplest and least expensive type, they operate at only one speed. Single-stage units can cool or heat a home efficiently. Two-stage compressors operate at two different speeds, more closely matching their cooling or heating output to the exact needs of the home. The ability to run at a lower, more efficient speed helps remove excess humidity from the air while saving energy and the compressor can switch to its full capacity if needed to hold temperatures steady. Two-stage systems are typically more energy-efficient than single-stage systems. Variable-capacity compressors provide exceptional control of home temperatures and humidity, because instead of operating at one or two settings, they can modulate their capacity in very small increments throughout a wide operating range. This allows for very precise control of cooling and heating, keeping temperatures even throughout the home and saving energy in the process. While variable-capacity systems tend to be more expensive, they provide exceptional savings on monthly energy bills and can be up to twice as efficient as single-stage models.

Difference Between Star and Delta Connection ! By Imran

Difference Between Star and Delta Connection are as

The terminals of the three branches are connected to a common point. The network formed is known as Star Connection. The three branches of the network are connected in such a way that it forms a closed loop known as Delta Connection. In a star connection, the starting and the finishing point ends of the three coils are connected together to a common point known as the neutral point. But in Delta connection, there is no neutral point. The end of each coil is connected to the starting point of the other coil that means the opposite terminals of the coils are connected together. In Star connection, the line current is equal to the Phase current, whereas in Delta Connection the line current is equal to root three times of the Phase Current. In Star connection, line voltage is equal to root three times of the Phase Voltage, whereas in Delta Connection line voltage is equal to the Phase voltage. The Speed of the star connected motors is slow as they receive 1/√3 of the voltage but the Speed of the delta connected motors is high because each phase gets the total of the line voltage. In Star Connection, Phase voltage is low as 1/√3 times of the line voltage, whereas in Delta Connection Phase voltage is equal to the line voltage. Star Connections are mainly required for the Power Transmission Network for longer distances, whereas in Delta connection mainly in Distribution networks and is used for shorter distances. In Star Connection, each winding receives 230 volts and in Delta Connection, each winding receives 415 volts. Both 3 phase 4 wire and 3 phase 3 wire system can be derived in the star connection, whereas in Delta Connection only 3 phase 4 wire system can be derived. The amount of Insulation required in Star Connection is low and in Delta Connection high insulation level is required.

PCB fault recognise ! By Imran

Chemical fluid leakage How To Recognise Five of the Most Common PCB FailuresThe presence of any chemical fluid that has leaked from a component can seriously damage the PCB and cause failure. Most chemicals are removed in the manufacturing process, but often trace elements are left behind. Inside the packaging of a component, leaks can happen, which cause rapid aging of the semiconductor or package. This chemical leakage can eventually cause shorts or become corrosive.

Issues with the soldering process Solders are the part that provides the necessary means of contact between the component and the circuit, without it the PCB would not work. There are a few solder issues that can cause failure, but the most common are flux contamination and poor processing conditions. Some flux residues can absorb moisture which can become conductive, causing short circuits. If the solder process is not properly set up and controlled, it can lead to open joints and contaminated solder Component barrier breakage The barrier of a component is there to protect the component from the outside environment and also to give a way for the component to connect to the circuit. If this barrier is broken, then the component will become exposed to environmental factors such as oxygen and humidity, which can cause the component to age and then fail. Physical problems with materials The materials used in a PCB can often encounter problems that will cause the board to fail. During the manufacturing stages, if a layer of the PCB is misaligned it will cause short circuits, open circuits and crossed signal lines. If there are psychical defects with the materials such as fractures, voids and delaminations they will seriously affect the performance of the PCB. Failure can also happen if the materials used are impure

Symptoms of Heat stress ! By Imran

The most common signs and symptoms of heat exhaustion include: Confusion Dark-colored urine (a sign of dehydration) Dizziness Fainting Fatigue Headache Muscle or abdominal cramps Nausea, vomiting, or diarrhea Pale skin Profuse sweating Rapid heartbeat Treatment for Heat Exhaustion If you, or anyone else, has symptoms of heat exhaustion, it's essential to immediately get out of the heat and rest, preferably in an air-conditioned room. If you can't get inside, try to find the nearest cool and shady place. Mohammad Imran (HVAC Engineer)

Heat load Calculation in very easy steps/By Imran

For an air conditioner to cool a room or building its output must be greater than the heat gain. It is important before purchasing an air conditioner that a heat load calculation is performed to ensure it is big enough for the intended application. Heat load calculations There are several different methods of calculating the heat load for a given area: Quick calculation for offices For offices with average insulation and lighting, 2/3 occupants and 3/4 personal computers and a photocopier, the following calculations will suffice: Heat load (BTU) = Length (ft.) x Width (ft.) x Height (ft.) x 4 Heat load (BTU) = Length (m) x Width (m) x Height (m) x 141 For every additional occupant add 500 BTU. If there are any additional significant sources of heat, for instance floor to ceiling south facing windows, or equipment that produces lots of heat, the above method will underestimate the heat load. In which case the following method should be used instead. A more accurate heat load calculation for any type of room or building The heat gain of a room or building depends on: The size of the area being cooled The size and position of windows, and whether they have shading The number of occupants Heat generated by equipment and machinery Heat generated by lighting By calculating the heat gain from each individual item and adding them together, an accurate heat load figure can be determined. Step One Calculate the area in square feet of the space to be cooled, and multiply by 31.25 Area BTU = length (ft.) x width (ft.) x 31.25 Step Two Calculate the heat gain through the windows. If the windows don’t have shading multiply the result by 1.4 North window BTU = Area of North facing windows (m. sq.) x 164 If no shading, North window BTU = North window BTU x 1.4 South window BTU = Area of South facing windows (m. sq.) x 868 If no shading, South window BTU = South window BTU x 1.4 Add the results together. Total window BTU = North window + South window Step Three Calculate the heat generated by occupants, allow 600 BTU per person. Occupant BTU = number of people x 600 Step Four Calculate the heat generated by each item of machinery - copiers, computers, ovens etc. Find the power in watts for each item, add them together and multiply by 3.4 Equipment BTU = total equipment watts x 3.4 Step Five Calculate the heat generated by lighting. Find the total wattage for all lighting and multiply by 4.25 Lighting BTU = total lighting watts x 4.25 Step Six Add the above together to find the total heat load. Total heat load BTU = Area BTU + Total Window BTU + Occupant BTU + Equipment BTU + Lighting BTU Step Seven Divide the heat load by the cooling capacity of the air conditioning unit in BTU, to determine how many air conditioners are needed. Number of a/c units required = Total heat load BTU / Cooling capacity BTU --------------------------------------------- MOHAMMAD IMRAN (HVAC Engineer)

HVAC top 35 questions likely to asked in interview

1.Question 1. What Is Local Comfort Cooling System? Answer : They may be integrated, with heating, ventilation and air conditioning provided by a single system, for example, air handling units connected to ductwork, or they may be a combination of separate systems, for example mechanical ventilation but with radiators for heating and local comfort cooling units. 2.Question 2. What Is Centralised Air System? Answer : The most common central cooling system is a split system, which includes an outdoor cabinet containing a condenser coil and compressor, and an indoor evaporator coil, usually installed in conjunction with your furnace. or air handler . The compressor pumps a chemical called refrigerant through the system. 3.Question 3. What Is Constant Volume System? Answer : Constant Air Volume (CAV) is a type of heating, ventilating, and air-conditioning (HVAC) system. In a simple CAV system, the supply air flow rate is constant, but the supply air temperature is varied to meet the thermal loads of a space. Most CAV systems are small, and serve a single thermal zone. 4.Question 4. What Is Variable Air Volume System & Dual Duct System? Answer : Variable Air Volume (VAV) is a type of heating, ventilating, and/or air-conditioning (HVAC) system. Unlike constant air volume (CAV) systems, which supply a constant airflow at a variable temperature, VAV systems vary the airflow at a constant temperature. 5.Question 5. What Is Hydronic System Or Air-water System? Answer : Hydronic systems circulate hot water through warming baseboards, radiators and/or radiant tubing in your floors or ceilings. There are many advantages to heating your home using a hydronic system, whether it is for a new home or as a replacement heating system. 6.Question 6. How Vapour Compression Cycle Works ? Answer : The Vapor-Compression Refrigeration Cycle is comprised of four steps. ... The condenser is in contact with the hot reservoir of the refrigeration system. (The gas releases heat into the hot reservoir because of the external work added to the gas.) The refrigerant leaves as a high pressure liquid. 7.Question 7. What Is Vapor Compression Cycle? Answer : Vapor-Compression Refrigeration or vapor-compression refrigeration system (VCRS), in which the refrigerant undergoes phase changes, is one of the many refrigeration cycles and is the most widely used method for air-conditioning of buildings and automobiles. 8.Question 8. Why Is A Compressor Used In Refrigeration? Answer : The compressor does exactly as its name says: it compresses the refrigerant. The compressor receives low pressure gas from the evaporator and converts it to high pressure gas. As mentioned earlier, as the gas is compressed, the temperature rises. The hot refrigerant gas then flows to the condenser. 9.Question 9. What Is Auto Refrigeration? Answer : Auto-refrigeration is a process where an unintentional and/or uncontrolled phase change of a hydrocarbon from a liquid state to a vapor occurs, resulting in a very rapid chilling (refrigeration) of the liquid containing local equipment and/or piping. 10.Question 10. How Does A Refrigerant Compressor Work? Answer : oThe compressor constricts the refrigerant vapor, raising its pressure, and pushes it into the coils on the outside of the refrigerator. o When the hot gas in the coils meets the cooler air temperature of the kitchen, it becomes a liquid. oThe refrigerant absorbs the heat inside the fridge, cooling down the air. 11.Question 11. Why Capacity Of Air Conditioner Is Measured In Tons? Answer : A 4 ton air conditioner is one that can remove 48,000 BTUs of heat per hour from the house. For most people, though, 4 tons means 8000 pounds. (A BTU is a British Thermal Unit, approximately the amount of heat you get from burning one kitchen match all the way down.) 12.Question 12. What Is The Meaning Of 1 Ton Of Ac? Answer : A ton, as used in the HVAC field, is a term that describes how much heat the AC unit can remove from a home in one hour. The measurement for heat is the British thermal unit (BTU). One ton of air conditioning can remove 12,000 BTUs of air per hour. 13.Question 13. What Is An Air Conditioning Ton? Answer : A ton is the cooling capacity of an air conditioning system. One ton is equal to the amount of heat required (288,000 Btu) to melt one ton of ice in a 24-hour period. A one-ton air conditioner is rated at 12,000 Btu per hour (288,000/24). A two-ton unit would be rated at 24,000 Btu per hour. 14.Question 14. What Is Btu? Answer : The British thermal unit (Btu or BTU) is a traditional unit of heat; it is defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit. ... Heat is now known to be equivalent to energy, for which the metric unit is the joule; one BTU is about 1055 joules. 15.Question 15. What Is The Meaning Of Btu In Air Conditioners? Answer : Btu – British Thermal Unit (Btu) is the international measure of energy. A Btu is the amount of heat needed to raise 1 (one) pound of water by 1(one) degree Fahrenheit. In HVAC industry, Btu's measure the quantity of heat a conditioning unit can remove from a room per hours. One BTU per hour is equal to 0293 watts. 16.Question 16. What Is Cfm & Infiltration? Answer : The infiltration rate is the volumetric flow rate of outside air into a building, typically in cubic feet per minute (CFM) or liters per second (LPS). The air exchange rate, (I), is the number of interior volume air changes that occur per hour, and has units of 1/h. 17.Question 17. What Is The Hvac System? Answer : While the Energy Center usually tries to avoid the use of acronyms, HVAC is in common use in the heating and cooling industry. It stands for "heating, ventilation and air conditioning," three functions often combined into one system in today's modern homes and buildings. 18.Question 18. What Does A Hvac Engineer Do? Answer : An HVAC engineer's job duties can include the design, installation, maintenance, and repair of heating, ventilation, air conditioning, cooling, and refrigeration systems. 19.Question 19. What Is Psychometry? Answer : Psychometry is a psychic ability in which a person can sense or "read" the history of an object by touching it. Such a person can receive impressions from an object by holding it in his/her hands or, perhaps, touching it to the forehead. 20.Question 20. What Are The Types Of Air Conditioning Systems? Answer : Types of Air Conditioning Systems The choice of which air conditioner system to use depends upon a number of factors including how large the area is to be cooled, the total heat generated inside the enclosed area, etc. o Window Air Conditioner. o Split Air Conditioner. o Packaged Air Conditioner. o Central Air Conditioning System. 21. Question 21. How The Lighting Load Is Calculated? Answer : The standard method consists of three calculation steps: General lighting VA load. When calculating branch circuits and feeder/service loads for dwellings, include a minimum 3VA per sq ft for general lighting and general-use receptacles [220.12]. When determining the area, use the outside dimensions of the dwelling. 22.Question 22. What Is The Function Of Ahu? Answer : An Air Handling Unit (AHU) is used to re-condition and circulate air as part of a heating, ventilating and air-conditioning system. The basic function of the AHU is take in outside air, re-condition it and supply it as fresh air to a building. 23.Question 23. How Does The Ahu Work? Answer : An air handler is usually a large metal box containing a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers. Air handlers usually connect to a ductwork ventilation system that distributes the conditioned air through the building and returns it to the AHU. 24.Question 24. What Is The Purpose Of Air Handling Units? Answer : An air handler, or air handling unit (often called an AHU), is used to condition and circulate air as part of an HVAC system. An air handler usually contains a blower, heating or cooling elements, filter racks or chambers, sound attenuators, and dampers. 25.Question 25. Where The Fcu’s Are Used? Answer : A fan coil unit is a simple device consisting of a heating or cooling coil and fan. It is part of an HVAC system found in residential, commercial, and buildings. Typically a fan coil unit is not connected to ductwork and is used to control the temperature in the space where it is installed, or serve multiple spaces. 26.Question 26. What Is The Fcu? Answer : A Fan Coil Unit (FCU) is a simple device consisting of a heating and/or cooling heat exchanger or 'coil' and fan. It is part of an HVAC system found in residential, commercial, and industrial buildings. 27.Question 27. What Is The Meaning Of Fahu? Answer : FAHU is the abbreviation used for FRESH AIR HANDLING UNIT. These are usually centralized units employed to induce fresh air quantities to the confines spaces. They come into picture wherever there are limitations to fresh air intake either directly or through AHUs. 28.Question 28. What Is An Air Conditioner Condenser? Answer : The AC condenser is a very important component found on virtually all modern automotive AC systems. Its primary function is to convert the refrigerant coming from the compressor from a high temperature, high pressure vapor into a high pressure liquid through condensation. 29.Question 29. how Does A Condenser In A Refrigerator Work? Answer : In the refrigeration cycle, there are five basic components: fluid refrigerant; a compressor, which controls the flow of refrigerant; the condenser coils (on the outside of the fridge); the evaporator coils (on the inside of the fridge); and something called an expansion device. 30.Question 30. What Is The Main Function Of A Condenser? Answer : In systems involving heat transfer, a condenser is a device or unit used to condense a substance from its gaseous to its liquid state, by cooling it. In so doing, the latent heat is given up by the substance, and will transfer to the condenser coolant. 31.Question 31. How Does A Condensing Unit Work? Answer : Inside the condenser, the refrigerant vapor is compressed and forced through a heat exchange coil, condensing it into a liquid and rejecting the heat previously absorbed from the cool indoor area. The condenser's heat exchanger is generally cooled by a fan blowing outside air through it. 32.Question 32. What Are The Types Of Condensers? Answer : The three main types of condensers used in general refrigeration systems are: o air-cooled. o water-cooled. o evaporative. 33. Question 33. What Is A Rotary Air Compressor? Answer : A rotary-screw compressor is a type of gas compressor that uses a rotary-type positive-displacement mechanism. They are commonly used to replace piston compressors where large volumes of high-pressure air are needed, either for large industrial applications or to operate high-power air tools such as jackhammers. 34.Question 34. What Is A Gas Compressor Used For? Answer : A gas compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor. Compressors are similar to pumps: both increase the pressure on a fluid and both can transport the fluid through a pipe. 35.Question 35. What Is The Use Of Compressor In Refrigeration? Answer : The compressor does exactly as its name says: it compresses the refrigerant. The compressor receives low pressure gas from the evaporator and converts it to high pressure gas. As mentioned earlier, as the gas is compressed, the temperature rises. The hot refrigerant gas then flows to the condenser.------------- Mohammad Imran HVAC Engineer

Types of hazards

Some items are hazardous by nature, while others only become hazardous if used inappropriately or carelessly. Often, accidents don’t just happen – they are a result of workers neglecting or ignoring hazardous situations. There are two basic categories of hazard: Acute hazard Acute hazards are those that have an obvious and immediate impact. Chronic hazard Chronic hazards have a more hidden, cumulative, long-term impact. An example of an acute hazard is a slippery floor where there is an immediate danger of someone slipping and being injured. A chronic hazard could be workplace bullying, where the long-term impact may result in stress or other psychological injury. Hazards generally fall into one of six groups: Physical – Slippery floors, objects in walkways, unsafe or misused machinery, excessive noise, poor lighting, fire. Chemical – Gases, dusts, fumes, vapours and liquids. Ergonomic – poor design of equipment, workstation design, (postural) or workflow, manual handling, repetitive movement. Radiation – Microwaves, infra-red, ultraviolet, lasers, X-rays and gamma rays. Psychological – Shiftwork, workload, dealing with the public, harassment, discrimination, threat of danger, constant low-level noise, stress.

Why oil return in refrigerant

The oil return in refrigeration systems is of key importance for the service life of the compressor and thus for a secure constant supply of refrigeration. In most compressors some lubrication oil is carried along with the compressed refrigerant. In the liquid refrigerant the oil is dissolved in the refrigerant and is transported without problems. In the vaporised refrigerant the oil remains liquid in the lower parts of the system. This can result in lack of oil in the compressor. To return the oil to the compressor, a minimum velocity must be maintained in the pipes. If the velocity in the rising pipe on the intake side of the compressor is too low (partial load), the oil is not returned to the compressor due to its higher density. The velocity in the rising pipe depends on the pipe diameter and the refrigerant mass flow. A small diameter of the rising pipe results in a high velocity and ensures the return of the oil even under partial load. However, at full load the pressure loss increases due to the small diameter. To compensate for this disadvantage, double rising pipes are used. During partial load oil gathers in a bend at the bottom of the double pipe. The oil in the bend blocks one of the two pipes so that the refrigerant flows at high velocity through the other pipe and transports the oil to the compressor. At full load the oil in the bend is pressed upwards so that the refrigerant flows through both pipes. Mohammad Imran HVAC Engineer