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systems analysis and design
Heating Ventilating And Air Conditioning Analysis And Design 6th Edition Faye C. McQuiston, Jerald D. Parker, Jeffrey D. Spitler - Solutions
=+3-35.Rework Problem 3-34 for an elevation of 5000 feet.
=+3-36. A building has a total heating load of 200,000 Btu/hr. The sensible heat factor for the space is 0.8 and the space is to be maintained at 72 F db and 30 percent relative humidity. Outdoor air at 40 F db and 20 percent relative humidity in the amount of 1000 cfm is required. Air is sup-plied
=+3-37. Reconsider Problem 3-36 for an elevation of 5000 feet.
=+3-38. The system of Problem 3-34 has a supply air fan located just downstream of the cooling coil.The total power input to the fan is 4.0 hp. It is also estimated that heat gain to the supply duct system is 1000 Btu/hr. Rework Problem 3-34 using Chart la, taking the fan and duct heat gain into
=+3-39.An evaporative cooling system is to be used to condition a large warehouse located in Denver, Colo ., (elevation = 5000 ft or 1500 m). The space is to be maintained at 80 F (27 C) and 50 percent relative humidity by a 100 percent outdoor air system. Outdoor design conditions are 90 F (32 C)
=+3-40.The summer design conditions for Shreveport, La ., are 95 F (35 C) db and 77 F (25 C) wb tem-perature. In Tucson, Ariz ., the design conditions are 102 F (39 C) db and 65 F (18 C) wb temperature. What is the lowest air temperature that can theoretically be attained in an evapo-rative cooler
=+3-41.A cooling system is being designed for use at high elevation (5000 ft or 1500 m) where the outdoor air is very dry. The space with a high latent load, SHF = 0.7, is to be maintained at 75 F (24 C) db and 40 percent relative humidity. Outdoor air at 100 F (38 C) and 10 percent relative
=+3-42.Consider a space heating system designed as shown in Fig. 3-21. The total space beating load is 500,000 Btu/hr (145 kW), and the space design conditions are 70 F (21 C) and 30 percent relative humidity (RH), Outdoor air enters the preheat coil at 6 F (-14 ℃) and essentially 0 per-cent RH
=+3-43.A variable-air-volume (VAV) cooling system is a type where the quantity of air supplied and the supply air temperature are controlled. The space is to be maintained at 75 F (24 C) db and 63 F (17 C) wb. Under design conditions, the total cooling load is 15.0 tons (53.0 kW) with a sensible
=+3-44. Rework Problem 3-43 for an elevation of 5000 feet (1500 m).
=+3-45. The design condition for a space is 77 F (25 ℃) db and 50 percent relative humidity with SS F(13 C) db supply air at 90 percent relative humidity. A 50-ton, constant-volume space air-conditioning system uses face and bypass and water temperature control. Outdoor air is sup-plied at 95 F
=+3-46. Rework Problem 3-45 for an elevation of 5000 feet (1500 m)
=+3-47.It is necessary to cool and dehumidify air from 80 F db and 67 F wb to 60 F dh and 54 F wh
=+(a) Discuss the feasibility of doing this in one process with a cooling coil. (HINT: Determine the apparatus dew point temperature for the process.) (b) Describe a practical method of achiev-ing the required process and sketch it on a psychrometric chart.
=+3-48.Conditions in one zone of a dual-duct conditioning system are to be maintained at 75 F (24 ℃)and 50 percent relative humidity (RH). The cold deck air is at 52 F (11 C) and 90 percent RH.while the hot deck air is outdoor air at 90 F (32 C) and 20 percent RH. The sensible heat fac-tor for
=+3-49.Rework Problem 3-48 for an elevation of 5000 ft (1500 m).
=+3-50.A water coil in Problem 3-48 cools return air to the cold deck condition. Determine the coil load (for the one zone) and sketch the processes for the entire system on a psychrometric chart.Find the volume flow rate entering the coil in (a) English units and (b) SI units.
=+3-51.A multizone air handler provides air to several zones. One interior zone contains computer equipment with only a sensible load. The coil in the unit cools air from 85 F (29 C) db and 70 F (21 C) wb to 53 F (12 C) db and 90% relative humidity (RH), (a) If the zone is to be main-tained at 75 F
=+ The amount of air supplied to the zone is 2.500 cfm (1.18 m3/s). (b) What is the cooling load for the zone? Assume standard sea-level pressure.
=+3-52.Under normal operating conditions a zone has a total cooling load of 120,000 Btu/hr (35 KW)with a SHF of 0.8. The space is to be maintained at 74 F (23 C) db and 50% relative humidity(RH). However, there are periods when the latent load is high and the SHF is estimated to be as low as 0.6.
=+(b) Define the various air states and show the processes on Chart la. (c) Compute air-flow rate, coil load, minimum zone load, and any reheat that may be required. Assume constant air flow and standard sea-level pressure.
=+3.53.An interior zone of a large building is designed to have a supply air-flow rate of 5000 cfm(2.4 m /s). The cooling load is constant at 10 tons (35 kW) with a SHF of 0.8 year-round. Indoor conditions are 75 F (24 C) db and 50 percent relative humidity (RH), (a) What is the maximum air dry
=+ (b) Consider a different time when the outdoor air has a temperature of 40 F (4 C) db and 20 percent relative humidity. Return air and outdoor air may be mixed to cool the space, but humidification will be required. Assume that saturated water vapor at 14.7 psia (101 kPa) is used to humidify the
=+(d) What is the refrigeration load for the coil of part (c) above?
=+3-54. Outdoor air is mixed with room return air to reduce the refrigeration load on a cooling coil.(a) For a space condition of 77 F (25 ℃) db and 68 F (20 C) wb, describe the maximum wet bulb and dry bulb temperatures that will reduce the coil load. (b) Suppose a system is designed to supply
=+3-55 Consider an enclosed swimming pool. The pool area has a sensible heat loss of 424,000 Btu/hr(124 kW) and a latent heat gain of 530,000 Bru/hr (155 kW) on a design day when the outdoor
=+air is at 35 F (2 C) and 20 percent relative humidity (RH). The space is to be maintained at 75 F(24 C) and 50 percent RH. Outdoor air is to be heated to 60 F (16 C), mixed with recirculated air from the conditioned space and the mixed air heated to supply conditions. (a) At what rate, in cfm, is
=+3-56.One particular zone served by a multizone air handler has a design cooling load of 1750 Btu/hr(0.5 kW) with a SHF of 0.8. The coil has air entering at 84 F (29 C) db and 70 F (21 C) wb with air leaving at 50 F (10 C) db and 90% relative humidity (RH). Zone conditions are 75 F(24 C) db and
=+3-57.A research building requires 100 percent outdoor ventilation air 24 hours a day. This causes a high latent cooling load relative to the sensible load. The peak cooling load is 100,000 Btw/hr(29.3 kW) with a SHF of 0.5. A coil configuration available has an apparatus dew point tem-perature of
=+3-58.A space requires cooling in the amount of 120,000 Btu/hr (35.2 kW) with a SHF of 0.5. Room conditions are 75 F (24 C); 50 percent relative humidity (RH). Outdoor air conditions are 90 F db and 75 F wb (32 C db and 24 C wb, respectively). One-third of the supply air is outdoor air.The coil
=+4-1.Using Fig. 4.1. draw a conclusion about the comfort of a mixed group of men and women in typical seasonal clothing, with sedentary activity for the following cases:(a) Summer, operative temperature 77 F, wb 64 F(b) Winter, operative temperature, 77 F. wb 64 F(c) Summer, operative temperature
=+4-2.Using Fig. 4-1. draw a conclusion about the comfort of a mixed group of men and women in typical seasonal clothing, with sedentary activity for the following cases:(a) Summer, operative temperature 24 C, wb 18 ℃(b) Winter, operative temperature 24 C, wb 18 C(c) Summer, operative temperature
=+4-3.Select comfortable summer design conditions (dry bulb and relative humidity) for a machine shop where people in light clothing (clo = 0.5) will be engaged in active work such as ham-mering, sawing, and walking around (met = 1.8). Begin by selecting an operative temperature from Fig. 4-1.
=+44 It is desired to use a space as a large classroom some of the time and a basketball court other times. What thermostat settings would you recommend in summer and winter for each type of use?
=+Assume that the relative humidity can be maintained at 40 percent all of the time, includ-ing for basketball: met = 3.0 and clo = 0.2.
=+4-5.An indoor tennis facility finds that it has excessive electrical charges for air conditioning the courts to a temperature that is comfortable for its players (68 F or 20 C). Overhead fans will increase the average air velocity at court level from zero to 100 fpm (0.50 m/s). What new
=+4-6.Work Problem 4-5 for an average air speed at court level of 200 fpm (1.0 m/s). After doing that(assuming no radiant effect) compute a temperature assuming that the mean radiant tempera-ture is 9 F (5 C) above the air temperature.
=+4-7.In an occupied space the mean air velocity is found to be 40 fpm (0.2 m/s), the dry bulb tem-perature is 74 F (23 C) and the globe temperature is measured to be 78 F (26 C). Calculate the operative temperature in both F and C.
=+4-8. An occupied space is being held at 76 F (24 C) and 50 percent relative humidity. A measure-ment of the globe temperature gives 80 F (27 C), and the mean air velocity is determined to be 30 fpm (0.15 m/s). Is this facility comfortable for sedentary functions of a mixed group in light clothing
=+4.9.What do you think is the best thermostat setting (air dry bulb temperature) in a shop where the workmen are standing, walking, lifting, and performing various machining tasks?
=+ Assume that a globe temperature measurement reads 72 F (22 C), the relative humidity will be in the 45 per-cent range, and air motion will likely be around 30 ft/min (0.15 m/s). The men are dressed in typical summer garments (clo = 0.5), Calculate the answer in F or C.
=+4-10. With the air conditioning running and the thermostat set at 78 F the wet bulb temperature is found to be 68 F in an office space. Assuming no significant radiant effects, would you expect the occupants to be comfortable in the summer'? If not, comment on any remedial action you might
=+4-11.Discuss how an emergency government mandate to set all thermostats at 65 F (18 C) for win-tertime heating would affect the following classes of people: (a) a person dressed in a business suit and vest, (b) a typist who basically sits all day, (c) a worker on an automobile assembly line, (d)
=+4-12. In the heating seasons the heat loss from a building (and thus the heating cost) is strongly dependent on the difference between the indoor and outdoor temperature. If the average out-door temperature in a particular city during the heating season is 45 F (7 C), what is the effect on
=+4-13. Air motion can be good or bad, depending on the air temperature. Discuss the general effect of increased or decreased air motion when the space temperature is (a) low in winter and (b) high in the summer.
=+4-14. To save energy in large, chilled water systems, the water temperature delivered to the cooling coils can be increased. A larger quantity of warmer supply air can remove the same energy from a space as a smaller quantity of cooler air. What could happen to the humidity of the space?Are there
=+4-15.Overhead fans (Casablanca fans) are often reversed in the wintertime to give air flow in a reversed direction to that of the summer time. Explain why this operation can make these fans useful in both warm and cool seasons.
=+4-16.A school classroom is designed for 30 people. (a) What is the minimum amount of clean out-door air required? (b) If the outdoor air ventilation requirement was based on floor area and the classroom contained 500 square feet, what rate of air would be required?
=+4-17.Carbon dioxide is being generated in an occupied space at the rate 0.25 cfm (0.118 l/s) and out-door air with a CO, concentration of 220 ppm is being supplied to the space at the rate of 900 cfm (0.425 m3/s). What will be the steady-state concentration of CO, in ppm if complete mix-ing is
=+4-18.Each person in a room is assumed to be producing carbon dioxide at the average rate of 0.0107 cfm (5.0 ml/s) and air with a CO, concentration of 280 ppm is being supplied to the room at the rate of 6000 cfm (2.8 m /s). It is desired to keep the concentration level of CO, in the space below
=+4-19.An air-handling system must handle 2000 cfm with a pressure drop of 0.25 in, wg available for the filter. The depth of the filter needs to be 8 inches or less. Select a filter system that will have a gravimetric efficiency of at least 95 percent in the particle size range of 0-5 × 10-3 mm.
=+4-20.Work Problem 4-19, assuming that the system must handle 1.00 m3/s with a pressure drop of 60 Pa. The filter must be less than 0.2 m in depth.
=+4-21. How many filter modules will be required using the M-2 media (see footnote in Table 4-3) in the size 12 x 24 x 8 if the pressure drop across the clean filter must be 0.10 in. wg or less when the air flow is 5500 cfm? What would be the face velocity at the filter?
=+4-22.Work Problem 4-21 assuming that the filter is a 0.3 x 0.6 x 0.2 and the pressure drop must be less than 24 Pa when the air flow is 2.8 m3/s.
=+4-23.The M-200, 0.6 x 0.6 x 0.2 filters of Table 4-3 are to be used with a system having a volume flow rate of 0.40 m2/s. What pressure drop across the clean filter and what filter face velocity would be expected?
=+4-24. Investigate the feasibility of using 100 percent outdoor in the cooling and dehumidifying of a laboratory whose computed heat gain is 3 tons and whose sensible heat factor is 0.7. The indoor design conditions are 78 F db and 40 percent relative humidity. The outdoor design conditions ure 95
=+4-25.Work Problem 4-24 but replace the 100 percent outdoor air requirement with 25 percent out-door air and use high-performance filters for the return air. Gravimetric efficiency must be at least 99 percent in the 0-5 x 10-6 meter particle range. (a) Find the required air flow and(b) design the
=+4-26.Using M-15 filter media and the requirement of 60 cfm per person of outdoor air for the case of a designated smoking area for 55 persons, design a filter and air-circulation system allow.ing the actual outdoor air rate to be reduced to 20 cfm per person. Assume outdoor and recir-culated air
=+4-27. A filter system is available that will filter out 80 percent of the tobacco smoke present in the air stream. Assume that the outdoor-like (fresh) air rate supplied to a smoking room must be 25 cfm and that 15 efm of actual outdoor air must be utilized. With that information, compute the
=+4-28.A maximum of 10 smokers are anticipated in a smoking room and cach is expected to con-tribute about 150 ug/min of environmental tobacco smoke (ETS) to the space. It is desired to hold the particulate level of ETS below 180 g/m' using filters with an effective efficiency of 80 percent and an
=+4-29.Solve Ex. 4-4 assuming that the filter is in location A in Fig. 4-9.
=+4-30.Solve Problem 4-28 assuming that the filter is in location A in Fig. 4-9.
=+4-31.For a 3000-ft' combination gym and exercise operation, it is desired to reduce the outdoor air intake rate to a minimum by filtering and air recirculation. (a) Design a system using filters having an efficiency of 0.50 and a pressure loss of 0.14 in. wg at 350 fu/min face velocity. Pres-sure
=+4.32 A classroom with a capacity of 225 people is isolated from the outdoors except for the incom-ing ventilation air. The cooling load is 125,000 Btu/hr (37 kW) with a sensible heat factor of 0.7. The minimum 15 cfm/person (7,5 L/s per person) is assumed adequate, (a) Compute the required amount
=+. (b) What is the minimum air supply rate based on indoor air quality requirements? (e) Compare parts (a) and (b) and discuss the best course of action.
=+5-1. Determine the thermal conductivity of 4 in. (100 mm) of insulation with a unit conductance of 0.2 Btu/(hr-ft2-F) [1.14 W/(m2-C)] in (a) English units and (b) SI units.
=+5-2.Compute the unit conductance C for 52 in. (140 mm) of fiberboard with a thermal conductive ity of 0.3 Btu-in./(hr-ft2-F) [0.043 W/(m-C)] in (a) English units and (b) SI units.
=+5-3.Compute the unit thermal resistance and the thermal resistance for 100 ft2 (9.3 m2) of the glass fiberboard for Problem 5-2 in (a) English units and (b) SI units.
=+5-4.What is the unit thermal resistance for an inside partition made up of 3 in. gypsum board on each side of 6 in. lightweight aggregate blocks with vermiculite-filled cores?
=+5-5.Compute the thermal resistance per unit length for a 4 in. schedule 40 steel pipe with 1 } in. of insulation. The insulation has a thermal conductivity of 0.2 Btu-in /(hr-ft2-F)-
=+5.6.Assuming that the blocks are not filled, compute the unit thermal resistance for the partition of Problem 5-4,
=+5-7.The partition of Problem 5-4 has still air on one side and a 15 mph wind on the other side.Compute the overall heat-transfer coefficient.
=+5-8.The pipe of Problem 5-5 has water flowing inside with a heat-transfer coefficient of 650 Btu/(hr-ft2-F) and is exposed to air on the outside with a film coefficient of 1.5 Btu/(hr-fr .F).Compute the overall heat-transfer coefficient based on the outer area.
=+5.9. Compute the overall thermal resistance of a wall made up of 100 mm brick (1920 kg/m') and 200 mm normal weight concrete block with a 20 mm air gap between. There is 13 mm of gp sum plaster on the inside. Assume a 7 m/s wind velocity on the outside and still air inside.
=+5-10.Compute the overall heat-transfer coefficient for a frame construction wall made of brick vencer (120 Ibm/ft') with 3 in. insulation bats between the 2 x 4 studs on 16 in. centen; Be wind velocity is 15 mph.
=+5-11. Estimate what fraction of the heat transfer for a vertical wall is pure convection using the data in Table 5-26 for still air. Explain
=+5-12.Make a table similar to Table 5-4a showing standard frame wall construction for 2 × 4 studs on 16 in. centers and 2 × 6 studs on 24 in. centers. Use 3 2 in. and 5 2 in. fibrous glass insula-tion. Compare the two different constructions.
=+5-13.Estimate the unit thermal resistance for a vertical 1.5 in. (40 mm) air space. The air space is near the inside surface of a wall of a heated space that has a large thermal resistance near the outside surface. The outdoor temperature is 10 F (-12 C). Assume nonreflective surfaces,
=+5-14.Refer to Problem 5-13, and estimate the unit thermal resistance assuming the air space has one bright aluminum foil surface.
=+5-15.A ceiling space is formed by a large flat roof and horizontal ceiling. The inside surface of the roof has a temperature of 145 F (63 C), and the top side of the ceiling insulation has a tem-perature of 110 F (43 C). Estimate the heat transferred by radiation and convection separately and
=+5-16.A wall is 20 ft (6.1 m) wide and 8 ft (2.4 m) high and has an overall heat-transfer coefficient of 0.07 Btu/(hr-ft2-F) [0.40 W/(m2-C)]. It contains a solid urethane foam core steel door.80 × 32 × 14 in. (203 × 81 x 2 cm), and a double glass window, 120× 30 in. (305 × 76 cm).The window
=+5-17.Estimate the heat-transfer rate per square foot through a flat, built-up roof-ceiling combination similar to that shown in Table 5-4b, construction 2. The ceiling is a in. acoustical tile with 4 in.fibrous glass batts above. Indoor and outdoor temperatures are 72 F and 5 F, respectively.
=+5-18.A wall exactly like the one described in Table 5-4a, construction 1, has dimensions of 15 x 3 m.The wall has a total window area of 8 m2 made of double-insulating glass with a 13 mm air space in an aluminum frame without thermal break. There is a urethane foam-core steel door without thermal
=+5-19.Refer to Table 5-4a, construction 2, and compute the overall transmission coefficient for the same construction with aluminum siding, backed with 0.375 in. (9.5 mm) insulating board in place of the brick.
=+5-20.Compute the overall heat-transfer coefficient for a 1% in. (35 mm) solid core wood door, and compare with the value given in Table 5-8.
=+5-21.Compute the overall heat transfer for a single glass window, and compare with the values given in Table 5-5a for the center of the glass. Assume the thermal conductivity of the glass is 10 Btu-in./(hr-ft2-F) [1.442 W/(m2-C)].
=+5-22.Determine the overall heat-transfer coefficient for (a) an ordinary vertical single-glass window with thermal break. (b) Assume the window has a roller shade with a 3, in. (89 mm) air space between the shade and the glass. Estimate the overall heat-transfer coefficient.
=+5-23. A basement is 20 x 20 ft (6 x 6 m) and 7 ft (2.13 m) below grade. The walls have R-4.17(R-0.73) insulation on the outside. (a) Estimate the overall heat-transfer coefficients for the walls and floor. (b) Estimate the heat loss from the basement assuming it is located in Chicago.IL. Assume a
=+5-24. Estimate the overall heat-transfer coefficient for a 20 x 24 ft (6 × 7 m) basement floor 7 ft (2 m)below grade that has been covered with carpet and fibrous pad.
=+5-25.Rework Problem 5-23 assuming that the walls are finished on the inside with R-11 (R-2) insu-lation and g in. (10 mm) gypsum board. The floor has a carpet and pad.
=+5-26. A heated building is built on a concrete slab with dimensions of 50× 100 ft (15 × 30 m). The slab is insulated around the edges with 1.5 in. (40 mm) expanded polystyrene, 2 ft (0.61 m) in width. The outdoor design temperature is 10 F (-12 C). Estimate heat loss from the floor slab.
=+5-27. A basement wall extends 6 ft (1.8 m) below grade and is insulated with R-12.5 (R-2.2). The inside is finished with sin, (12,7 mm) insulating board, plastic vapor seal, and , in. (6 mm)plywood paneling. Compute the overall heat-transfer coefficient for the wall,
=+5-28.A 24 × 40 ft (7.3 × 12.2 m) building has a full basement with uninsulated walls extending 5 ft(1.5 m) below grade. The insides of the walls are finished with R-8 (R-0.7) insulation, a thin vapor barrier, and sin, (12.7 mm) gypsum board. Estimate an overall heat-transfer coefficient for the
=+5-29.The floor of the basement described in Problem 5-28 is finished with a thin vapor barrier, fin.(16 mm) particle-board underlayment, and carpet with rubber pad. Estimate an overall heut-transfer coefficient for the floor.
=+5-30. Assume that the ground temperature 1, is 40 F (10 C) and that the inside temperature is 68 F(20 C) in Problem 5-28 and estimate the temperature between the wall and insulation and between the gypsum board and insulation.
=+5-31. Use the temperatures given in Problem 5-30 and compute the temperature between the under-layment and the carpet pad in Problem 5-29.
=+5-32.A small office building is constructed with a concrete slab floor. Estimate the heat loss per unit length of perimeter. Assume (a) R-5 (R-0.88) vertical edge insulation 2_ft (60 cm) wide;
=+(b) edge insulation at slab edge only. Assume an outdoor design temperature of 5 F (-15 C)and indoor temperature of 70 F (21 C).
=+5-33.A 100 ft length of buried, uninsulated steel pipe carries chilled water at a mean temperature of 42 F. The pipe is 30 in. deep and has a 4 in. diameter. The thermal conductivity of the earth is about 8 Btu-in./(hr-ft -- F). Assume the temperature of the ground near the surface is 70 F and
=+5-34.Estimate the beat loss from 100 m of buried hot-water pipe. The mean water temperature is 60 C. The copper pipe with 20 mm of insulation, k = 0.05 W/(m-C), is buried 1 m below the surface and is 50 mm in diameter. Assume a thermal conductivity of the earth of 1.4 W/(m-C)and a ground surface
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