Document KKdwJeyovDnBn9OnzGXdBOqr

438 CHAPTER 30 put from that panel. The required panel output is given in the following table. Available Panel Area Sq Ft Required Panel Output, qj Btu/(hr) (sq ft) 1960 Guide Room A 132 sq ft Room B 127 sq ft 2500 Tif " 19 7 Room C 306 sq ft 8000 306 " Step 5. Panel Surface Temperature From Fig. 15 find the panel surface temperature needed to yield the required heat output to each room, using the output determined in Step 2 and the design room air temperature. This use of Fig. 15 for Room A is illustrated in Fig. 15A. Rg. 18 .... Upward Heat Flow from Plaster Ceiting Panel The values of o for Rooms A, B, and C as determined from Fig. 18 are as follows: Room A B C U 0.25 0.25 0.05 4-4 F Deg 42 20 97 ft. Btu/(hr)(sq ft) 12.5 6.0 5.0 Rg. 15A .... Determination of Panel Surface Temperature for Room A from Rg. 15 The values of 4 determined for Rooms A, B, and C are as follows: Room A 4 " F Room B 4 -- 92 F Room C 4 - 97 F Step 4. Upward Heat Flow Determine the upward heat Sow from each panel using Fig. 18. The upward heat flow must be determined in order to ob tain the downward panel resistance and to select the proper stse of boiler. The use of Fig. 18 is illustrated for Room A in Fig. 18A. Note that the U values shown on Fig. 18 are those Step 6. Downward Panel Resistance Assume tentative pipe or tube spacings for the panel con struction to be used from those listed in Table 1, choosing the closer spacings when higher outputs are required. Also in Table 1 find the resistance of eacn panel (r*), using heat flow ratios calculated from the flow rates determined in Steps 2 and 4, interpolating as required. Room Spacinq Heat Flow Ratio Resistance (u) (Inches) A 4tf 0.35 B 9 it,-0-30 0.90 C 9 -- - 0.19 0.85 26.1 Step 6. Mean Water Temperature For the required panel output ($*) found in Step 2, the panel resistance (r<) found in Step 5, and the room air temperature (4), find the mean water temperature (4.) from Fig. 15. This use of Fig. 15 is illustrated in Fig. 15B. Rg. 18A .... Determination of Upward Heat Row for Room A from Rg. 18 far the entire structure of which the panel is a part and are taken from room air (temperature, 4) to air above the panel (temperature, 4) and for that reason qm y* C/(4 -- 4)- U values maybe obtained from Chapter 9, Heat Transmission Coeffi cients of Building Materials. Rg. 15B .... Determination of Mean Water Temperature for Room A from Rg. 15 Panel Heating Table 1___ Thermal Resistance of Plaster and Metol Ceiling Panels 439 Values of 4 for Rooms A, B, and C as determined from Fig. 15 are as follows. Room A tmm ** 131 F, Room B 4* " 110.5 F, Room C 4* = 119 F Step 7. Design Mean Water Temperature Select a single design mean water temperature (4) for each group of rooms which is to comprise a tone, choosing the highest mean water temperature (4) of the group subject to the following: a. If 4> + ^ is equal to or less than 4., (see No menclature and Table 1, this mean water temperature (4) is an acceptable design mean water temperature (4m)- Pro ceed to Step 8. b. If 4 + ^ ^ ^ is greater than t-- , go back to Step 5 and select a panel construction which has a lower panel re sistance (r<). This can be accomplished by either or both of the following: 1. Reducing the tube spacing, 2. Decreasing the upward heat flow (g.) by providing ad ditional insulation above the panel. If the required mean water temperature is still too high apply either or both of the following: 1. Reduce the heat loss of the room, 2. Provide supplementary heating. In Example 1, assume 4 -- 4 = 15 F deg and 4u -- 140 F. TheD since 4 " 131 F, 4 + M (4 -- 4) 138.5 F and is less than 4 - Thus 131 F can be used as the design mean water temperature 4m . Step i. Design Panel Output From Fig. 15, find the panel output (q<) for design mean water temperature (4m). room air temperature (4), and pane) resistance (r*). Fig. ISC shows bow Fig. 15 is used to find qe for Room B in this step. Rg. 15C .... Determination of Design Panel Output for Room B from Rg. 15 The mean water temperature (4W) found for Room A iD Step 6 was used as the design mean water temperature (4m). The panel output for Room A which was determined in Step 2 is therefore tne design panel output for this room. Design panel outputs for Rooms B and C can be found from Fig. 15 using the design mean water temperature (4m)- Room Design Panel Output (g<) Btu per (hr) (sq ft) A 47.7 B 32.5 C 33.0