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102 EGEE Quiz 8 The compressor of a heat pump system ___________ the pressure of the refrigerant, ________ its temperature. Answer: increases, raising Flat plate collectors are usually placed on the roof or ground in the sunlight. They are classified as a(an) _____. Answer: Active system What is the most commonly used fuel for residential heating? Answer: Gas Using kitchen and bath exhaust fans may adversely affect the heating and cooling requirements. Register to View AnswerWhere there is limited space, a hydronic heating system can be installed vertically. Register to View AnswerA GHP can be installed vertically if there is limited space. A hydronic heating system must be installed horizontally underneath the floor to be effective. There is no reason to ventilate the attic in the summer if it is well insulated. Register to View AnswerVentilating the attic in the summer lets the hot air to escape. What is the typical range for the COP for heat pumps? Answer: 1.5 3.5 When a heat pump is used to heat a house in winter, how is the Coefficient of Performance affected as the outside temperature drops? Answer: Decreases Radiant floor systems heat _____. Answer: the entire floor A house that effectively uses passive solar heating and cooling will_____. Answer: Face south and have deciduous trees growing on the south side to block heat in the summer and allow sunlight in the winter. Bleeding air from the pipes of a hydronic radiant baseboard heating system will _____. Answer: Increase efficiency Which one of the following devices may heat as well as cool a house? Register to View Answerheat pump An active system emits more SO2 directly into the environment than a passive system. Register to View AnswerBoth the active and passive systems use solar energy, which do not directly emit SO2 energy into the environment. A heat pump (heating) with a COP of 2.8 maintains an indoor temperature of 67 degrees F. What is the outside temperature (in oF)? Answer: 67 oF = (67 - 32) 5 / 9 oC = 19.44oC = 19.44 + 273 K= 292.44 K ' 2.8 = 292.44 / (292.44 - tcold) tcold = 292.44 - 292.44 / 2.8 = 187.99 K = 187.99 - 273 oC = -85.01 oC = (-85.01 x 9 / 5) + 32 oF = -121.02 oF Horizontal loop Geothermal heat pumps are used when there is less space available Register to View AnswerVertical loop Geothermal heat pumps are used when there is less space available Using kitchen and bath exhaust fans may adversely affect the heating and cooling requirements Register to View AnswerWhich of the following items is used in a passive solar heating system? Answer: Flat plate collectors AFUE stands for _____. Answer: Annual Fuel Utilization Efficiency Which of the following is not true about a geothermal heat pump? Answer: Its cost is a hindrance for their development Which one of the following items is used in a passive solar heating system? Answer: South facing windows Solar and GHP heating systems have absolutely no impact on the environment. Register to View AnswerBoth solar and GHP heating systems both require the use of pumps that use electricity. Although the amount is small, it is still electricity, and with generation of electricity, there are emissions. In heating mode when the refrigerant liquid moves past the expansion valve it_____. Answer: evaporates, absorbing heat from the outside What happens when the outside temperature falls below the 'Balance Point'? Answer: the heat pump output falls below the home heating requirement The work (energy) input to a heat pump system is at the _____. Answer: Compressor A heat mover _____. Answer: uses work to move heat from a low temperature reservoir to a high temperature reservoir In a baseboard radiator, _________increase(s) the surface area, which in turn leads to more efficient heat transfer. Answer: Fins What happens to the high temperature, high pressure refrigerant after it comes out of the compressor of a heat pump (heating mode)? Answer: It condenses in the coil, giving off heat to the inside When a heat pump is used to heat a house in the winter, how will the Coefficient of Performance be affected if the outside temperature increases? Answer: It increases What is the typical cost of natural gas per million BTUs? Answer: $11 One of the heating systems we talked about in this course comprises of a system of ducts. What is the process by which heat is transferred in this system? Answer: Convection The average cost of electricity in the US is ______. Answer: $80/MWh What type of air system is most commonly used in central heating and cooling systems? Answer: Forced Air Duct The home heating and cooling system is the major residential user of energy Register to View AnswerOn a summer afternoon you should keep the draperies closed on all west-facing windows to block out the hot sun Register to View AnswerInsolation is a combination of the following words _____. Answer: Incident solar radiation Which term is used to describe the efficiency of a Central Air Conditioner? Answer: SEER Ground Source heat pumps are less efficient than air to air heat pumps. Register to View AnswerGround source heat pumps are more efficient than air to air heat pumps High temperature, high pressure refrigerant comes out of the compressor and _____. Answer: condenses, giving off heat to the inside Of the following, which one is not an advantage of forced air heating systems? Answer: They usually have a very high efficiency (80-90%) If a heat pump is used to heat a house in the winter, how will the Coefficient of Performance be affected as the outside temperature drops? Answer: It decreases. Installation of a GHP costs $8,500, whereas the installation of a forced air system costs $4,000. The average cost of heating using a GHP is $55/month and the average cost of heating using a forced air system costs $145/month. After 5 years, which is cheaper, and by how much? Answer: GHP, $900. Find each total cost by using: installation + (cost/month*12months/year*5years). subtract Then the lowest from the highest Which one of the following is an example of thermal mass? Answer: Stone Horizontal loop geothermal heat pumps are used when there is less space available. Register to View AnswerVertical loop geothermal heat pumps are used when there is less space available Which term is used to define the energy efficiency of a central air-to-air Heat Pump? Answer: HSPF In home heating, if the outside temperature increases, holding the inside temperature constant, the Coefficient of Performance of a heat pump decreases. Register to View AnswerBalance point - the temperature at which the heat pump output and home heat requirements match, occurs when _____. Answer: the heat pump output falls below the home heating requirement A freezer maintains a temperature of 30F while the outside temperature is 75F. What is the COP of the freezer cooling system? Answer: COP = Thot/(Thot-Tcold) Tcold = 30 F = (30-32)x5/9 C = -1.11 C = -1.11 + 273 K = 271.89 K Thot = 75 F = (75-32)x5/9 C = 23.89 C = 23.89 + 273 K = 296.89 K COP = 296.89/(296.89-271.89) = 11.87 Thermal-lined draperies and outdoor awnings can significantly reduce the energy required for air conditioning. Register to View AnswerNearly one half of the energy used at home is for _____. Answer: Space heating and cooling When looking at a graph of BTUs/h and outdoor temperature, the amount of supplemental heat (in BTUs) can be determined by_____. Answer: subtracting home heating requirement BTU point for a specific temperature by the heat pump output BTU point for the same temperature, to the left of the balance point One of the heating systems we talked about in this course comprises of a system of ducts. What is the process by which heating occurs in this system? Answer: Convection What is the process by which forced-air furnace systems distribute heat? Answer: Convection We know that, electrical resistance heating systems approach an efficiency of 97%. Electrical baseboard heating is more efficient than a heat pump. Register to View AnswerA heat mover speeds up a natural heating process. Register to View AnswerAll of the following are examples of ways to improve energy efficiency of heating systems, except _______. Answer: Opening the front door in winter to filter and clean warm air. If a heat pump is used to heat a house in the winter, how will the Coefficient of Performance be affected if the inside set temperature is changed from 70 F to 65 F? Answer: It increases Which one of the following energy sources is used by the most efficient heating systems? Answer: Electricity All air-source heat pumps are rated by "heating season performance factor" (HSPF) Register to View AnswerOpening the drapes of windows on which side of a house helps in heating? Answer: south When using a fire place, most of the heated air is lost through the chimney. Register to View AnswerWhen a heat pump is used to heat a house in the winter, how will the coefficient of performance be affected if the inside set temperature is changed from 65 F to 70 F? Answer: It decreases Of the following sources, where does a typical home loses most heat? Answer: Cracks in walls, windows, and doors. Compared to a house built in the 1960's, a house built today has _____ Register to View Answergreater R-value Electrical resistance heating systems approach an efficiency of 97%. This makes electrical baseboard heating more efficient than a heat pump. Register to View AnswerWhich one of the following is true about a geothermal heat pump? Answer: It saves energy and the environment What is the physical meaning of the coefficient of performance? Answer: it is the amount of heat moved between the reservoirs for every unit of work done. Most of the energy used at home is used for _____. Answer: heating Bleeding air from the pipes of a hydronic radiant baseboard heating system _____. Answer: increases efficiency A "desuperheater" can provide a homeowner with _____. Answer: free or reduced cost hot water Due to convection, a house with an electric radiant system and floors with a high thermal mass can reduce heating costs if the electric company offers "time-of-use" rates. Register to View AnswerWhat is the name given to the weatherization process used in sealing cracks in windows, doors and walls? Answer: caulking Ground Source heat pumps are more efficient than air to air heat pumps. Register to View AnswerThe coefficient of performance for a single heat pump in heating mode is greatest at which temperature? Answer: 50F The collector's efficiency increases as ______. Answer: useful energy delivered increases (insolation remains constant) The temperature inside a home remains at 70F. If on Tuesday the temperature outside is 55F, but then on Wednesday the temperature outside is 35F, what is the percent change in COP? (Round your answer to the nearest whole number) Answer: 59% decrease. By plugging the numbers into the COP equation, it is found that an outside temperature of 55F produces a COP of 37 and an outside temperature of 35F produces a COP of 58. Then finding the percent change from the first to the second results in -59%. Due to convection, a house with an electric radiant system and floors with a high thermal mass, can reduce heating costs if the electric company offers "time-of-use" rates. Register to View AnswerWhich one of the following will have a negative impact on the home heating efficiency? Answer: Open front door in winter to filter and clean warm air. Solar and GHP heating systems have absolutely no impact on the environment. Register to View AnswerKeep the draperies and shades on your south-facing windows open during a _____________ day to cut down energy costs. Answer: Winter What is nearly half of the energy used at home used for? Answer: space heating and cooling The furnace/air conditioner will run for longer periods of time when the air filter is dirty. Register to View Answer ... View Full Document

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