Fiauro 1oboathe saturation vapour pressure (e,), as a function of air Lantern Festival 2021 1. Determine e, when T 12C, T = 25C, and T 34C. Enter the values in Table 1. 2. Frequently the atmosplhere is not saturated such that the actual vapour pressure (ea) is less than the e, for the current temperature. Also, Ta is the temperature to which the air must be cooled for saturation to occur. For example, using tlhe graph, at an ca of 10mb, Ta = 7.5C. Using these relationships, complete the missing valnes in Table 1. Table 1: Atmospheric Humidity Parameters T.(CC) Ta( C) ,(mb) Ca(mb) RH(%) 12 25 23 34 80 Open with Part 3: Applications 1. Given an 1800 hour surface temperature of 8C and that the air adja- cent to the surface has a RH = 70%, at what time will condensation occur if the evening cooling rate is 1C/hr? Will the surface conden- Lantern Festival 2021 h the form of dew or frost? %3D 2. In continental interior areas of Canada, winter air is often very cold and dry. Suppose the outside air temperature is -10C and the RH = 70%. The outside air is now heated to 20C inside a building. What will be the new RH and what are the implications for human working conditions inside the building? %3D 70 Lartern Fest val 2021 50 SATURATION VAPOUR PRESSURE, e. (mb) Table 2: Psychrometric Table (RH%) (T-Tu) 0.5 1.0 1.5 2.0 2.5 3.0 4.0 5.0 6.0 8.0 10.0 54 64 58 67 61 Lantern Festival 2021 0.0 75 100 92 83 100 92 84 100 93 86 61 42 31 22 47 37 51 42 67 7 2 70 73 100 93 87 81 100 94 88 82 77 28 14 4 79 33 20 6 76 69 64 71 78 73 54 46 38 25 15 66 57 49 69 60 76 29 42 19 52 45 33 10 100 94 88 83 24 12 100 95 89 84 79 75 70 62 55 48 37 28 14 100 95 90 85 81 76 82 72 77 64 57 51 40 31 16 100 96 90 86 74 78 83 66 60 54 43 34 45 18 100 9G 91 20 100 97 86 83 75 68 62 56 37 91 87 79 76 69 63 58 48 39 22 100 97 92 87 84 80 77 71 65 59 50 41 24 100 97 92 100 98 92 100 98 88 85 78 72 66 61 51 43 26 88 85 82 79 73 67 62 53 45 28 93 89 86 83 30 100 98 80 74 68 63 55 47 93 100 98 100 98 86 93 90 87 89 80 75 69 65 70 32 56 18 34 84 76 66 57 50 93 90 87 36 100 98 82 76 71 67 58 51 94 100 98 91 85 82 77 72 73 38 94 91 68 59 52 86 83 78 8 53 Page 4 I 5 + Part 1: Measurement of Humidity Atmoxpheric hummidity has traditionally been measured with the wet-und- dy bulb paychtometer. The wet-bullb thermometer is kept wet with a cotton wick, nud the evaporation fron the wick alsorbes laten heat and lowers the lantein Festival 2021 thermometer reads. The evaporation rate depends on the Tumidity in the surrounding air. The difference between the dry-bulb (T,) and the wet-bullb (T) temper- atures (T,- T) - known as the wet-bulb depression the evaporation and hence the humidity in the atmosphere. Knowing the T, and Tw, we can determine the relative humidity directly off of the the psychrometie table ('Table 2). is a mensIure of 1. Using a psychrometer, record T, T, and the wet-bull depression (T T) both inside the classroom and outside the building. Compare with what other colleagues got. 2. Use the psychrometric table to determine the relative humidity for cach location.