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 HVAC interview questions and answers 1.  What is ASHRAE &  ISHRAE?   American Society of Heating Refrigeration and Air-conditioning Engineers. Indian Society of Heating, Refrigerating and Air Conditioning Engineers. 2. What is COP and  Relative COP?  COP -  Coefficient Of Performance COP =Net Refrigeration Effect / Work Done Supplied It is the parameter on which efficiency is compared to air-conditioning units. It is calculated at 100% load. Relative COP =  ratio of actual COP and Theoretical COP 3.  What Is Btu? BTU = British thermal unit  It is the unit in which air-conditioning capacity defined. 1 TR = 12000 BTU/hr 4.Explain Refrigeration cycle?  Components that make a refrigeration system?. Watch the video with detailed explanation. 5. What Our Air Conditioning System and its function? and type of air-conditioning system? 6.  Which Gas used in   VRF? R410a 7. What is VRV and VRF?  http://learnhvac003.blogspot.com/2020/08/vrvvrf-overview.html 8. What is

Thermal Insulation   Thermal insulation is used in HVAC to avoided heat loss or heat gain from the duct of pipe. It also avoids condensation on cold surfaces. A heat-insulating material is one which has low thermal conductivity. Eg. 1. Duct carries chilled air from the AC unit to space, Heat loss or gain can change the temperature of the air  To avoid heat loss or gain, thermal insulation is used 2. Pipe  Chilled water pipe carrying water or refrigerant from one unit to other  to avoid Heat loss or gain, thermal insulation is used. Steam is generated in boiler and it is taken to the turbine through the pipe. To reduce heat loss or gain, insulation is used. Required Property on Insulating material 1. Can withstand high or low temperature 2. Should have a long life and can not be easily damaged. 3. Easy to install. 4.Should be economical. 5.Fire resistance. 6. resistance to Ozone and UV. Various material such as asbestos, glass wool, expanded polystyrene, puff, nitrile material is used f

  TR        -       Tons of Refrigeration - It Is a unit of refrigeration. -The rating of a refrigeration machine is given by a standard unit of refrigeration called Ton of Refrigeration. -One a ton of refrigeration (1TR) means the capacity to freeze 1 ton of water from and at 0’ in 24 Hrs. It's important to note that the freezing or melting of the ice represents a change-of-state only, which is considered a transfer of latent heat, as opposed to a change in temperature which is a transfer of sensible heat . Calculation • In USA 1 ton is taken as 2000lbs and its latent of fusion 144 B.Th. U/ lb  (334.9 KJ/Kg).                1 TR = (2000x144)/24                         = 12000 B  Th  U/ hr                         = 200 B  Th  U /Min                    1 B  Th  U =1.055 KJ                  1 TR =200 x1.055 KJ/Min                           = 211 KJ/Min                         1 TR = 3.517 KJ/s or KW Important Conversion   1 TR        =  12000 B  Th  U/ hr                  = 3.514 KW

  Thermodynamic System It is defined as quantity in space bounded by real or imaginary, fixed or movable boundaries across which energy take place from or to surroundings. External to the system is called surrounding or environment. A system with surrounding called a universe. Type of System Open System In this system, energy transfer takes place along with boundaries with mass transfer. Eg. Water in pool In pool mass and energy , both transfers can take place. Closed System In this system, energy transfer takes place with the outside environment through the boundary without mass transfer. Isolated System A system without mass and energy transfer is called an isolated system. Thermodynamic Equilibrium It is a state in which the system has a thermal and mechanical equilibrium. Energy It is the capacity to do work. Types of Energy Potential Energy It is the energy stored in an object due to its position relative to some zero position. Kinetic Energy It is the energy of a given mass due t

Fresh Air  -Outside air to that within the room or enclosed space. -Increase Indoor air quality by diluting enclosed polluted air in space. -Fresh air Increase room cooling load. -Increase the comfortable level of human. It depends on  -Occupancy -Area -Type of Use Youtube link on Fresh air  Fresh Air Standard Eg. Area -100 Sqft Occupancy-10 Nos Type of Use-Office FA -(0.06*100)+(5*10)           =56 CFM 2. Area -100 Sqft Occupancy-10 Nos Type of Use-Media Center FA -(0.12*100)+(10*10)           =112 CFM In-Duct type equipment fresh air mix with return air in mixing box or in AHU room then it passes through the coil and it will be distributed to space through the duct. Type of Fresh air -Normal air Normal outside air directly supplied to Air-Conditioning unit.   -Treated Fresh air  Treated Air (Chilled air) supplied to space. Thanks for giving your valuable time. Plz subscribe the channel and like the Facebook page YouTube-   https://www.youtube.com/watch?v=DkF9QAPOfIw and provide your

    What is Refrigeration? It is the process in which heat is removed from body or space in such a way that first its temperature reduced and then maintained at a level below surrounding. In this process heat is withdrawn from the desired space and rejected to the atmosphere which act as a natural receiver. Insulated material is used to avoid heat flow from surrounding to enclosed space which is maintained at a lower temperature.   Application 1.Manufacturing of ice. 2.Preservation of medicine. 3.For pre cooling and pasteurization of milk and in butter preparation. 4.cooling of cement concreate. 5.liquification of gases such as nitrogen, oxygen, hydrogen etc. 6.Preservation of fruits and vegetable, foods. What is Air-Conditioning?   It is the process in which temperature, moisture, air quality is controlled for an enclosed space depending on the requirement. It has two type 1.Comfort AC In this type different parameter of an enclosed space such as temperature, air