EBK THERMODYNAMICS: AN ENGINEERING APPR
8th Edition
ISBN: 8220100257056
Author: CENGEL
Publisher: YUZU
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Chapter 14.7, Problem 118RP
To determine
How much the trees will save the homeowner in the 20-year life of the system.
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1. A geothermal heat pump with a COP of 1.3 provides 48000 BTU/hr of heat to a
building. Assuming an electrical power rate of $0.20/kWh. answer the following
questions for this system:
a. What would be the monthly cost to provide heat at a rate of 48000 BTU/hr
if the heat was delivered by a simple electrical resistance heater?
b. How much heat is drawn from the ground by the heat pump in that month,
in kWh?
c. What is the savings per month enjoyed by operating this heat pump for a
month vs. a simple electrical resistance heater?
A food compartment is to be maintained at 21°C by a refrigeration system. The total cooling
load of the food compartment is estimated to be 330 kJ/h and the heat rejection by the
condenser is 480 kJ/h. The outdoor air temperature is 35°C.
draw the schematic diagram of the refrigeration system
determine the power input required to operate the refrigeration system in kW.
An air conditioner on a summer day removes heat steadily from a house at a rate of 750 kJ/min while drawing electric power at a rate of 5.25 kW. Please answer the following. a. Create a schematic representation of the air conditioning system under consideration. b. Determine the COP of this air conditioner and the rate of heat transfer to the outside air. c. Now winter has come, and the owner decides to use the equipment as heat pump to warm the house. Because the house is not perfectly insulated, and the outside temperature is 0°C the estimated rate of heat transfer loss rate from the house to the surroundings is equal to 1200 kJ/min. Will the air conditioning unit operating as heat pump satisfy the required heating if the electrical power drawn is 5.25 kW? Explain how you arrived at the answer. d. If the heat pump would operate as a Carnot Heat Pump and the indoor temperature is 25°C while the outside temperature is 0°C, compute the COP.
Chapter 14 Solutions
EBK THERMODYNAMICS: AN ENGINEERING APPR
Ch. 14.7 - What is the difference between dry air and...Ch. 14.7 - What is the difference between the specific...Ch. 14.7 - Can the water vapor in air be treated as an ideal...Ch. 14.7 - Is the relative humidity of saturated air...Ch. 14.7 - Is it possible to obtain saturated air from...Ch. 14.7 - Moist air is passed through a cooling section...Ch. 14.7 - How will (a) the specific humidity and (b) the...Ch. 14.7 - Prob. 8PCh. 14.7 - Consider a tank that contains moist air at 3 atm...Ch. 14.7 - Why are the chilled water lines always wrapped...
Ch. 14.7 - A tank contains 15 kg of dry air and 0.17 kg of...Ch. 14.7 - Prob. 12PCh. 14.7 - Prob. 13PCh. 14.7 - 14–13 A room contains air at 20°C and 98 kPa at a...Ch. 14.7 - A room contains air at 85F and 13.5 psia at a...Ch. 14.7 - An 8-m3 tank contains saturated air at 30C, 105...Ch. 14.7 - Prob. 17PCh. 14.7 - Prob. 18PCh. 14.7 - Prob. 19PCh. 14.7 - Andy and Wendy both wear glasses. On a cold winter...Ch. 14.7 - In summer, the outer surface of a glass filled...Ch. 14.7 - In some climates, cleaning the ice off the...Ch. 14.7 - Prob. 23PCh. 14.7 - Prob. 24PCh. 14.7 - Prob. 25PCh. 14.7 - Prob. 26PCh. 14.7 - A thirsty woman opens the refrigerator and picks...Ch. 14.7 - Prob. 28PCh. 14.7 - The air in a room has a dry-bulb temperature of...Ch. 14.7 - Prob. 31PCh. 14.7 - Prob. 32PCh. 14.7 - How do constant-enthalpy and...Ch. 14.7 - At what states on the psychrometric chart are the...Ch. 14.7 - How is the dew-point temperature at a specified...Ch. 14.7 - Can the enthalpy values determined from a...Ch. 14.7 - Prob. 37PCh. 14.7 - Prob. 39PCh. 14.7 - Prob. 41PCh. 14.7 - Prob. 42PCh. 14.7 - Prob. 43PCh. 14.7 - Prob. 44PCh. 14.7 - What does a modern air-conditioning system do...Ch. 14.7 - How does the human body respond to (a) hot...Ch. 14.7 - Prob. 47PCh. 14.7 - How does the air motion in the vicinity of the...Ch. 14.7 - Consider a tennis match in cold weather where both...Ch. 14.7 - Prob. 50PCh. 14.7 - Prob. 51PCh. 14.7 - Prob. 52PCh. 14.7 - What is metabolism? What is the range of metabolic...Ch. 14.7 - What is sensible heat? How is the sensible heat...Ch. 14.7 - Prob. 55PCh. 14.7 - Prob. 56PCh. 14.7 - Prob. 57PCh. 14.7 - Prob. 58PCh. 14.7 - Repeat Prob. 1459 for an infiltration rate of 1.8...Ch. 14.7 - An average person produces 0.25 kg of moisture...Ch. 14.7 - An average (1.82 kg or 4.0 lbm) chicken has a...Ch. 14.7 - How do relative and specific humidities change...Ch. 14.7 - Prob. 63PCh. 14.7 - Prob. 64PCh. 14.7 - Prob. 65PCh. 14.7 - Humid air at 40 psia, 50F, and 90 percent relative...Ch. 14.7 - Air enters a 30-cm-diameter cooling section at 1...Ch. 14.7 - Prob. 68PCh. 14.7 - Prob. 69PCh. 14.7 - Why is heated air sometimes humidified?Ch. 14.7 - Air at 1 atm, 15C, and 60 percent relative...Ch. 14.7 - Prob. 72PCh. 14.7 - An air-conditioning system operates at a total...Ch. 14.7 - Prob. 74PCh. 14.7 - Why is cooled air sometimes reheated in summer...Ch. 14.7 - Prob. 76PCh. 14.7 - Prob. 77PCh. 14.7 - Air enters a 40-cm-diameter cooling section at 1...Ch. 14.7 - Repeat Prob. 1479 for a total pressure of 88 kPa...Ch. 14.7 - Prob. 81PCh. 14.7 - Prob. 83PCh. 14.7 - Prob. 84PCh. 14.7 - Prob. 85PCh. 14.7 - Atmospheric air at 1 atm, 32C, and 95 percent...Ch. 14.7 - Prob. 88PCh. 14.7 - Prob. 89PCh. 14.7 - Does an evaporation process have to involve heat...Ch. 14.7 - Prob. 93PCh. 14.7 - Prob. 94PCh. 14.7 - Air at 1 atm, 20C, and 70 percent relative...Ch. 14.7 - Two unsaturated airstreams are mixed...Ch. 14.7 - Consider the adiabatic mixing of two airstreams....Ch. 14.7 - Prob. 98PCh. 14.7 - Two airstreams are mixed steadily and...Ch. 14.7 - A stream of warm air with a dry-bulb temperature...Ch. 14.7 - Prob. 104PCh. 14.7 - How does a natural-draft wet cooling tower work?Ch. 14.7 - What is a spray pond? How does its performance...Ch. 14.7 - The cooling water from the condenser of a power...Ch. 14.7 - Prob. 108PCh. 14.7 - A wet cooling tower is to cool 60 kg/s of water...Ch. 14.7 - Prob. 110PCh. 14.7 - Prob. 111PCh. 14.7 - Prob. 112PCh. 14.7 - Prob. 113RPCh. 14.7 - Prob. 114RPCh. 14.7 - Prob. 115RPCh. 14.7 - Prob. 116RPCh. 14.7 - Prob. 117RPCh. 14.7 - Prob. 118RPCh. 14.7 - Prob. 119RPCh. 14.7 - Prob. 120RPCh. 14.7 - 14–121 The relative humidity inside dacha of Prob....Ch. 14.7 - Prob. 122RPCh. 14.7 - Prob. 124RPCh. 14.7 - 14–126E Air at 15 psia, 60°F, and 70 percent...Ch. 14.7 - Prob. 127RPCh. 14.7 - Air enters a cooling section at 97 kPa, 35C, and...Ch. 14.7 - Prob. 129RPCh. 14.7 - Humid air at 101.3 kPa, 36C dry bulb and 65...Ch. 14.7 - 14–131 Air enters an air-conditioning system that...Ch. 14.7 - Prob. 132RPCh. 14.7 - Prob. 133RPCh. 14.7 - Conditioned air at 13C and 90 percent relative...Ch. 14.7 - Prob. 138RPCh. 14.7 - A room is filled with saturated moist air at 25C...Ch. 14.7 - Prob. 141FEPCh. 14.7 - A 40-m3 room contains air at 30C and a total...Ch. 14.7 - Prob. 143FEPCh. 14.7 - The air in a house is at 25C and 65 percent...Ch. 14.7 - On the psychrometric chart, a cooling and...Ch. 14.7 - On the psychrometric chart, a heating and...Ch. 14.7 - An airstream at a specified temperature and...Ch. 14.7 - Prob. 148FEPCh. 14.7 - Air at a total pressure of 90 kPa, 15C, and 75...
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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, mechanical-engineering and related others by exploring similar questions and additional content below.Similar questions
- A heat pump is used to extract heat from the outside atmosphere to heat the inside of a building. On a day when the outside air temperature is Tc°C, the heat pump is operating to a COP of 3.7, maintaining the inside temperature of the building at Th°C. If the building is losing heat at the rate of 53,709 kJ/hour in these conditions, determine how much power (kW) must be supplied to a heat pump? Keep two decimal placesarrow_forward14. A classroom that normally contains 40 people is to be air-conditioned with window air- conditioning units of 5- kW cooling capacity. A person at rest may be assumed to dissipate heat at a rate of about 360 kJ/h. There are 10 light bulbs in the room, each with a rating of 100 W. The rate of heat transfer to the classroom through the walls and the windows is estimated to be 15,000 kJ/h. If the room air is to be maintained at a constant temperature of 21°C, determine the number of window air-conditioning units required.arrow_forwardA parameter used to characterize the heat pump cycle performance is called the thermal efficiency. True or False?arrow_forward
- An absorption refrigeration system provides 24 kW of cooling while receiving 18 kW of solar heat input. The COP of this system is 1.0 1.33 0.75 0.5arrow_forwardA geothermal heat pump with a coefficient of performance of 1.3 supplies a building with 48000 BTU/hr of heat. Assuming a $0.20/kWh electricity rate. Provide responses to the following questions about this system: a. How much would it cost per month to supply heat at a rate of 48000 BTU/hr using a basic electrical resistance heater? b. In that month, how much heat is extracted from the earth by the heat pump, in kWh? c. What is the monthly savings associated with using this heat pump vs a basic electrical resistive heater?arrow_forwardBy supplying energy to a house at a rate of 25,000 kJ/hr, a heat pump maintains the temperature of the dwelling at 20 C when the outside air is at -10 C. If electricity costs 8 cents per kW-hr, determine the minimum theoretical operating cost to heat the house for 24 hours. $1.97 O $1.37 $1.75 O $1.51 O$1.64arrow_forward
- The roofs of many homes in the United States are covered with photovoltaic (PV) solar cells that resemble roof tiles, generating electricity quietly from solar energy. An article stated that over its projected 30-year service life, a 4-kW roof PV system in California will reduce the production of CO2 that causes global warming by 433,000 lbm, sulfates that cause acid rain by 2900 lbm, and nitrates that cause smog by 1660 lbm. The article also claims that a PV roof will save 253,000 lbm of coal, 21,000 gallons of oil, and 27 million ft3 of natural gas. Making reasonable assumptions for incident solar radiation, efficiency, and emissions, evaluate these claims and make corrections if necessary.arrow_forwardWhat are the magnitudes of the forces each worker must exert to load the refrigerators?arrow_forwardA regional electric utility company has a power plant with 1000 MW of electricity. The overall thermal efficiency of the power plant is 25%. The fuel used in the plant is an oil with a heating value of 5.00 ´106 kJ/kg and costs PHP 3.75 per liter. The density of the oil is 0.90 kg/L. Determine: (a) the daily fuel requirement (kg) when the plant runs at maximum capacity.(b) the daily fuel cost (PHP) of running the plant at maximum capacity.There are two answers: one for (a), one for (b).arrow_forward
- If a house needs a minimum heat transfer rate of 75 kJ/h (i.e., 75 kJ of heat needs to be transferred into the house during one hour) to maintain a pleasant indoor temperature. If one wants to use a heat pump with a COP of 5.55 to fulfill this heat transfer rate, what is the corresponding electricity (in kWh) consumption to run such a heat pump for one hour?arrow_forwardAfter a lengthy period of driving, you can feel how warm the engine is by placing your palm on the hood or even near to it. What kind (or types) of heat transfer are occurring?arrow_forwardA garage is being retrofitted with a heat pump of COP=3. The garage heat losses are 10,000 BTU/h. How much would it cost to heat for one month (30 days) if electricity costs $0.14/kWh? How much will it cost to heat with an electrical baseboard (assume 100% efficiency)? Ans: heat pump - around $100 (exactly $98.5); electrical baseboard - $295.40arrow_forward
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