It is well known that wind makes the cold air feel much colder as a result of the wind-chill effect that is due to the increase in the convection heat transfer coefficient with increasing air velocity. The wind-chill effect is usually expressed in terms of the wind-chill temperature (WCT), which is the apparent temperature felt by exposed skin. For an outdoor air temperature of 0 o C, for example, the wind-chill temperature is − 5 o C with 20 km/h winds and − 9 o C with 60 km/h winds. That is, a person exposed to 0 o C windy air at 20 km/h will feel as cold as a person exposed to − 5 o C calm air (air motion under 5 km/h). For heat transfer purposes, a standing man can be modeled as a 30-cm-diameter, 170-cm-long vertical cylinder with both the top and bottom surfaces insulated and with the side surface at an average temperature of 34 o C . and For a convection heat transfer coefficient of 15 W/m 2. K, determine the rate of heat loss from this man by convection in still air at 20 o C . and What would your answer be if the convection heat transfer coefficient is increased to 30 W/m 2. K as a result of winds? What is the wind-chill temperature in this case?
It is well known that wind makes the cold air feel much colder as a result of the wind-chill effect that is due to the increase in the convection heat transfer coefficient with increasing air velocity. The wind-chill effect is usually expressed in terms of the wind-chill temperature (WCT), which is the apparent temperature felt by exposed skin. For an outdoor air temperature of 0 o C, for example, the wind-chill temperature is − 5 o C with 20 km/h winds and − 9 o C with 60 km/h winds. That is, a person exposed to 0 o C windy air at 20 km/h will feel as cold as a person exposed to − 5 o C calm air (air motion under 5 km/h). For heat transfer purposes, a standing man can be modeled as a 30-cm-diameter, 170-cm-long vertical cylinder with both the top and bottom surfaces insulated and with the side surface at an average temperature of 34 o C . and For a convection heat transfer coefficient of 15 W/m 2. K, determine the rate of heat loss from this man by convection in still air at 20 o C . and What would your answer be if the convection heat transfer coefficient is increased to 30 W/m 2. K as a result of winds? What is the wind-chill temperature in this case?
It is well known that wind makes the cold air feel much colder as a result of the wind-chill effect that is due to the increase in the convection heat transfer coefficient with increasing air velocity. The wind-chill effect is usually expressed in terms of the wind-chill temperature (WCT), which is the apparent temperature felt by exposed skin. For an outdoor air temperature of
0
o
C,
for example, the wind-chill temperature is
−
5
o
C
with 20 km/h winds and
−
9
o
C
with 60 km/h winds. That is, a person exposed to
0
o
C
windy air at 20 km/h will feel as cold as a person exposed to
−
5
o
C
calm air (air motion under 5 km/h).
For heat transfer purposes, a standing man can be modeled as a 30-cm-diameter, 170-cm-long vertical cylinder with both the top and bottom surfaces insulated and with the side surface at an average temperature of
34
o
C
.
and For a convection heat transfer coefficient of 15 W/m2. K, determine the rate of heat loss from this man by convection in still air at
20
o
C
.
and What would your answer be if the convection heat transfer coefficient is increased to 30 W/m2. K as a result of winds? What is the wind-chill temperature in this case?
1.5 m^3/s of moist air at a state of 28°C DBT, 21°C WBT and 101.325 kPa flows across a cooler coil and leaves at 12.5°C DBT and 0.0083 kg/kg d.a.. Determine the following:
1. The apparatus dew-point temperature in °C using the psychrometric chart.
2. The By-pass factor in percentile
3. The cooling load of the process in kilowatts.
On a summer day in Phoenix, Arizona, the inside room temperature is maintained at 68° F while the outdoor air temperature is a sizzling 110° F . What is the outdoor– indoor temperature difference in (a) degrees Fahrenheit, (b) degrees Rankine, (c) degrees Celsius, and (d) kelvin? Is one degree temperature difference in Celsius equal to one temperature difference in kelvin, and is one degree temperature difference in Fahrenheit equal to one degree temperature difference in Rankine? If so, why?
1.5 m3/s of moist air at a state of 28°C DB, 21°C WB, and 101.325 kPa flows across a cooler coil and leaves at 12.5°C DB and 0.0083 kg/kg d.a. Determine the following:
A) The Apparatus Dew-Point Temperature in °C using the Psychrometric Chart.
B) The By-Pass Factor in Percentile (%).
C) The Cooling Load of the process in kilowatts.
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