Document mB7dLzjBVw39b5g8KkJ68kLkB

284 CHAPTER 19 1965 Guide And Data Book Table 5 .... Thermal Conductivity (fc) of Liquid Refrigerants* Refrigerant . Nemo r.,,Pj Thermal Conductivity, Refer- k 11 Trif-htoromonofluoro- f mM.hnn* | "68 . 0.0605 7 0.055 12 Dkhlorodifiuoro- j -4 0.0515 7 methane 1 68 0.042 13 taonochlorotrifiuoro- j 68 0.035 7 methane . \ 21 Dichkiroinonofluoro- ( -4 methane ) 68 22 Monochlorodifluoro- ( -4 methane \ 68 0.0715 0.065 0.0635 0.0525 7 7 * -- Btu per (boar) (cqoaro toot) (Fahrenheit decree per foot). No. 113 114 30 717 718 1120 Refrigerant Nome Trichlorotrifluoroethanel Dichlorotetrafluoroethane Methylene Chloride Ammonia Water Trichloroethylene . Jt -4 68 -4 68 5 86 5 86 32 100 122 Thermal k 0.048 0.0435 0.044 0.111 0.096 0.29 0.29 0.343 0.363 0.080 *"* 7 7 8 8 8 8 Table 6.... Thermal Conductivity (fc) of Refrigerant Vapors at One Atmosphere* Refrigerant No. Noma Temp* F Thermal Conductivity k Refer- No. Refrigerant Name Twnp, F. Conductivity Refer* k 11 Trichloromonofluoromethane 12 Dichlorodifluoromethane 22 Monochlorodiffuoromethane 113* Tricblorotrifluoroethane 114 Dichlorotetrafluoroethane 86 0.00505 b 30 Methylene Chloride 194 0.00621 . b . 32 / 32 0.0039 0.0053 40 Methyl Chloride 86 0.00591 b 170 Ethane ) 115 125 0.0072 0.0145 194 0.00738 b 600 Butane 32 0.0078 601 Isobutane 86 0.00675 b 32 0.0080 194 0.00824 b 717 Ammonia 86 0.00450 b 194 0.00631 b 744 Carbon Dioxide 1 32 i 122 I 302 32 0.0128 0.0157 0.0235 0.0085 744A Nitrous Oxide 122 0.0111 86 0.00627 194 0.00804 ce 1150 Ethylene 1 162 . i 306 0.0154 0.0226 8 8. 11 8 8 8 11 11 8 11 11 11 * k Bta per (hoar) (eqaare toot) (Fahrenheit decree per foot}* At one halt atmeepbem. * Average value baaed on data of Qefereneea 4 and 10. * Average value baaed ee data <f Befereoaee 9 and 11. circulated would be different, depending on the molecular weight. The compression ratio in centrifugal compressors is affected by the vapor density. The density is related to the molecular weight of the gas as well as the temperature and pressure of operation. PHYSICAL PROPERTIES Some physical properties of refrigerants are listed in Table 2. They are arranged there in increasing order of atmospheric boiling point. The viscosities of liquid and vapor are shown in Tables 3 and 4 and the thermal conductivity in Tables 5 and 6. HEAT PROPERTIES The heat capacities (specific heat) of liquid refrigerants are shown in Table 7 for several different temperatures. These values have been calculated from the heat content (enthalpy) data listed in the'tables of thermodynamic properties in Chapter 20. They are included here for ready reference and to illustrate the magnitude of differences among the various refrigerants. Values at other temperatures can be obtained from Chapter 20. The liquid heat capacity is involved in the refrigeration cycle as.'the condensed liquid is oooled to the evaporation temperature. It' is not often used directly in refrigeration calculations, but an appreciation of the amount of heat involved may help to explain differences in the per formance of different refrigerants, or of the same refrigerant at different temperatures. The vapor heat capacity also can be obtained from tahW of thermodynamic properties (Chapter 20). The heat capacity at constant pressure can be calculated as follows: Difference in Heat Content Between Two Temperatures at the Same Pressure Temperature Difference The heat capacity at constant volume can be calculated from the tables, although some interpolation is necessary: Difference in Heat Content\ (Between Two Temperatures j -- (0.1851 F)(AP) at the Same Volume / Temperature Difference' In Table 8 the effects of pressure and temperature on the heat capacity and the heat capacity ratio (cw'c.) are shown for several fluorinated refrigerants. The heat capacity at one atmosphere is illustrated in Table 0 for several fluorinated refrigerants and in Table 10 for some other refrigerants. Ah empirical rule of chemistry (Trouton's Rule)< is that the latent heat of vaporisation at the boiling point on a molar basis, divided by the temperature in absolute units, is a con stant for most materials.-This rule has been applied to re frigerants in Table 11. It holds fairly well for these refriger ants, although the result is not entirely constant. The rule is helpful in comparing different refrigerants and in understand ing the operation of refrigeration systems. ^ .* ELECTRICAL PROPERTIES The electrical characteristics of refrigerants are especially important in hermetic systems. Some properties for the liquid and vapor are shown in Tables 12 and 13. Refrigerants 285 Table 7 Heat Capacity of Liquid Refrigerants Bfw par f0>) (F dag) Refrigerant No. Name -30 F OF 11 Trichloromonofluoromethane Dichlorodifluoromethane 0.199 0.212 .13 Monochlorotrifluoromethane ' . 0.240 21 Dichloromonofluoromethane 22 Monochlorodifluoromethane 40 Methyl Chloride 113 Tnchlorotrifluoroethaae 114 Dichlorotetr&fluoroethane 0.234 0.257 0.357 0.195 0.208 0.200 0.216 0.260 0.238 0.268 0.365 0.202 0.217 500 ... 600 o-Butane 717 Ammonia** 744 Carbon Dioxide 0.258 1.05 0.45 0.268 0.48 1.10 0.48 * Data from E. L duPocrt de Naawure A Co., Im. Uoed by penaueeioa. t Data Iran General Chemical Divtaloa. Allied Chemical Carp. Uoed by pen&issioa. * Axeotrcpe af Refricerest 12 and 152a (73.8/20.2 percent by ^ifht). * For adtiUocal data, n Reference & 30 F 0.204 0.220 0.295 0.242 0.280 0.370 0.206 0.227 0.278 0.51 1.10 0.62 60 F 0-209 0.227 0.249 0.292 0.380 0.211 0.236 0.290 0.52 1.10 0.75 90 F 0.213 0.257 0.308 0.390 0.217 0.246 0.305 0.53 1.15 Refer- f 8 1 8 8 8 Table 8 .... Heat Capacity of-Refrigerant Vapors* Bfo per (lb) (F dag) Refripermd 12 13 12 22 12 13 freswv, pda 10 10 10 100 100 100 200 200 200 v 0.143 0.150 0.153" 50 F ft ep/ft 0.125 0.130 0.128 1.143 1.150 ;1.190 0.162 6.135 1.195 0.186 - * 0.142 1.310 * Data fnsn E. L daPottt de Nemoun A Co.. Ina. Deed by permiarioQ. ft 0.149 0.157 0.1C0 0.172 0.166 0.179 0.177 . 0.218 100 F ft 0.131 0.138 0.136 0.141 0.141 0.143 0.144 0.153 ft/ft 1.133 1.140 1.177 1.225 1.172 1.253 1.230 1.422 0.154 0164 0.166 0.168 0.170 0.180 0.178 0.201 ISO F ft 0.137 0.145 0.143 0.143 0.147 0.148 0.148 0.155 ft/ft 1.125 1.13 1.166 1.181 1.158 1.215 1.198 1.301 Table 9... .Vapor Heat Capacity of Fluorinated Refrigerants at One Atmosphere* Bto per (lb) (F dag) etrigeract 11 .21 22 113 114 ft 0.144 0.149 0.135 . . 50 F ft/ft . . 0.126 9-130. ` 1.148 1.15 0.114 0.129 1.186 1.195 0.155 ` 0.142 1.092 ft 0.140 0.150 0.157 0.142 0.160 0.162 100 F - c/ ' 0.125 0.132 0.137 0.121 0.136 0.149 ft/ft 1.13 1.136 1.14 1.172 1.180 1.087 ft 0 144 0155 0.164 0.149 0 167 0162 0.168 150 F ft 0.129 0.137 0-145 0.128 0.143 0.154 0.156 ft/ft 1.12 1.127 1.13 1.161 1.168 1.052 1.077 by r~~-^n Befriggract 11 (com General Chemical Drvman. Allied Chemical Corp. Data on other refrigerant* from E. L dnPant de Nemoun A Co.. lac. Ueed Table 10 . i.. Vapor Heat Capacity of Various Refrigerants at One Atmosphere Refrigerant* Ntx Name . Temperahare, F Bfw/l/h) (F deg) - ft ft/ft. 170 Ethane 59 ' 212 ' 1.22 1.19 717 / ;! 32 0.50` Ammonia* - i-v.,-59.;'- . 1.310. 1 'L.212 ij .0.53 For addittat*! data, ace Reference 6, ' "'lli ....... Refrigerant. Tempera- No.. - Name F* 744 1150 Carbon Dioxide ' | Ethylene j 32 59 212 59 212 fiiu/t/b) (F deg) ft ft/ft 0-205 0.215 1.304 . 1.255 .1.18