In the AHU shown in Figure 2, which has no preheat coil and operates at essentially 100% outdoor air at minimum flow, the freeze-stat would regularly trip when
outside air temperatures approached freezing.
This model includes blower, evaporator, heater core as well as the impact of important thermal loads such as sun radiation,
outside air temperature and passengers on climate control of cabin.
Not only does a whole-house fan cost less to run than air conditioning, but it can cool a house down in just a few minutes, after the
outside air temperature has decreased.
The showers, I was pleased to find out, were super powerful and super warm - just what I needed when the
outside air temperature was plummeting to -4c.
This process is known as radiant cooling, and while only a few degrees difference is needed, it's not uncommon for the aircraft skin to actually be as much as 5[degrees]C or, in very severe conditions, 10[degrees]C cooler than the
outside air temperature. This is why frost will readily form on an aircraft even when the
outside air temperature is as much as 4[degrees]C above zero.
Faxes arrive on his private combined fax machine, printer, copier and scanner, and a display showing the
outside air temperature and wind speed enables him check the weather without looking out the window.
Ryan found scientific studies showing that on a hot summer day the
outside air temperature in a city can be 2 to 6 degrees Celsius hotter than in the nearby countryside.
On the mid-January day when I visited, the
outside air temperature was just 7C, so it would not have been unreasonable to expect a chilly welcome.
A single thermocouple, located under a metal shield (i.e., covered) about 50 mm away (extending outside) from the back wall and about 2 m above the ground, was used to measure
outside air temperature. At each type-T thermocouple location, temperature data were collected every 5 minutes; an hourly average was recorded using a Campbell-Scientific (Logan, Utah) model CR 10 data logger and a model AM416, 32-channel multiplexer.
It is clear from Fig 2 that the heat flow densities on outer surfaces of the walls have the shape of summed
outside air temperature and solar radiation density curves and have 3-4 hours time-lag.
When the
outside air temperature is lower than the temperature of the required chilled water, instead of using the compressor (and energy) for cooling, the outside air is used instead.
Ries explained, "Our six-hour missions can be a hard slog in the middle of summer, where the
outside air temperature is regularly 120[degrees]F to 130[degrees]F.