(1) A hot-water boiler is consuming coal at the rate of 4 pounds per hour per square foot of grate surface. A low-pressure steam boiler is consuming coal at the rate of 8 pounds per hour per square foot of grate surface, and a steam boiler used for power purposes is consuming coal at the rate of 20 pounds per hour per square foot of grate surface. How many cubic feet of air at 62° F. are required to burn a ton of coal in each?

(2) A certain building requires a supply of heat amounting to 5,000,000 B. T. U. per hour to maintain a temperature of 70° when the outer air is at zero. The heat is to be obtained from steam having a temperature of 220°, and the air to be heated is taken from the outer atmosphere. The heating surfaces will be concentrated in the form of a vertical-tube heater as shown in Fig. 34, Heating and Ventilation of Buildings, and the velocity of the air through the heater will be 14 feet per second. How many feet of 1-inch tubes will be required for the heater? Consider 3 feet of 1-inch pipe equal to 1 square foot of surface. Ans. 9,090 ft. of pipe.

(3) Describe a disk fan. Is it suitable for ventilating large buildings? Give your reasons.

(4) What is an automatic air vent? Explain its use.

(5) Distinguish between high-pressure and low-pressure steam-heating systems. Which is more desirable for domestic purposes?

(6) (a) Explain how air locks are formed in hot-water heating systems, and state how they affect the circulation. (b) How can they be avoided?

(7) The length of the combined circuits of a hot-water heating apparatus is 800 feet. The radiators supplied by this apparatus are all 10 to 15 feet above the bottom of the boiler. What should be the diameter of the mains to supply 650 feet of radiation, allowing for 20° F. fall in temperature at the radiators? Ans. (i in.

(8) (a) Describe an inside cold-air duct and explain its use. (b) What should be the ratio between the sectional area of a cold-air duct and that of the hot-air flues?

(9) Distinguish between the exhaust and the pressure systems of ventilation.

(10) (a) Clearly define radiation, convection, and conduction of heat, (b) Would a polished nickel-plated cast-iron direct radiator be an efficient arrangement for heating the air in a room? Give reasons.

(11) Mention the chief points to be considered in selecting a fuel.

(12) Compute, by Baldwin's rule, the amount of direct radiation required to maintain a temperature of 70° in the room A, Fig. 36, Heating and Ventilation of Buildings, changing the dimensions (20 feet and 25 feet) to 30 feet and 35 feet, respectively; the sizes of the windows, height of ceilings, and all other conditions will remain the same as those given in Fig. 36. Divide the entire radiation between the radiators a and b.

(13) What must be considered in connecting two or more fans to the same conduit?

(14) What class of valves are best adapted to steam radiators? Describe them.

(15) Clearly describe the exhaust system of warming buildings by steam, and explain its usefulness.

(16) Describe the one-pipe system of hot-water heating, and mention its disadvantages.

(17) How many feet of hot-water direct radiation are required to heat an ordinarily well made and moderately exposed greenhouse to 60° F., when the outside temperature is zero? The greenhouse has 2,400 square feet of glass and 600 square feet of exposed wall surface.

Ans. 730 sq. ft., nearly.

(18) Three rooms, one on the first floor, one on the second floor, and one on the third floor, have precisely the same dimensions, glass and wall areas, and exposures. There are 50 square feet of glass surface and 240 square feet of exposed wall surface in each room, all exposures being very severe. What should be the diameters of the hot-air pipes for each room? Allow for a very short leader for the first floor and long leaders for the second and the third floor.

(19) Distinguish between natural-draft and forced-blast systems of ventilation. Which is the better system? Give reasons.

(20) A straight wrought-iron pipe 250 feet long is fitted up when its temperature is 60° F.; how much will it expand if filled with steam having a temperature of 307° F.?

Ans. 5.082 in.

(21) In designing a coal bin to contain 25 tons of anthracite coal (stove size), the length of the bin is 18 feet, and its depth is 6 feet; what should be its width, assuming that the bin is prismatic? Ans. 8 ft. 4 in.

(22) An exceedingly well built, lathed and plastered, sheathed and weather-boarded wooden wall, having an area of 875 square feet, allows 6,125 B. T. U. per hour to pass from the air in a room to the outer atmosphere. How many more B. T. U. would be lost per hour if an 8-inch brick wall were used instead, the temperature of the room being 70° and that of the outer air 0° F.? Ans. 22,050 B. T. U.

(23) In selecting a boiler, what should be considered regarding the direction of the flow of the gases?

(24) Clearly describe the one-pipe system of steam heating.

(25) Clearly describe the vacuum system of warming buildings by steam. What machine is necessarily required?

(26) What is the primary cause of circulation of water in a hot-water heating system?

(27) Fig. 1 is an elevation of a system of hot-water piping placed in a greenhouse. The flow main a is run overhead and the returns are run under the benches, as shown. It was found that after the system was filled with water and the fire started in the boiler d, the pipes would not heat.

Fig. 1.

Steam formed in the boiler and blew to the atmosphere from the expansion tank c. The pipes are properly proportioned, and there is ample heating surface under the benches.