They home in on the speed and cacophony of today's media environment, tossing participants into a virtual pressure
cooker of online outrage and escalating press attention.
Figure 3 shows a virtual pressure sensing line routed from the roof level exterior pressure reference down to the base of the building.
The corresponding change in pressure within the virtual pressure reference sensing line will be at a different rate than in the interior pressure reference sensing line whenever there is a difference between the interior air and exterior air temperatures.
The change in the pressure in the virtual pressure sensing line should be calculated from the base of the building to the roof line or at a point where the outdoor static pressure reference sensing line penetrates into the building.
Virtual pressure measurements for these locations are determined using refrigerant property relations.
Virtual pressure sensor outputs can be used in combination with other virtual sensors to provide a wealth of information for monitoring and diagnostics.
However, there are several technical issues that need to be considered, including 1) identifying suitable locations for mounting thermocouples that will ensure that refrigerant conditions are saturated for a wide range of driving conditions and in the presence of all kinds of faults, 2) accounting for the pressure drop between locations where temperatures are measured and the points where virtual pressure measurements are needed, and 3) evaluating the overall accuracy and impact on diagnostic performance of employing virtual pressure measurements.
Figure 5 illustrates the virtual pressure sensor development concept.
Estimates of refrigerant pressure drops can be used to estimate virtual pressure measurements from saturation pressures determined using the surface-mounted refrigerant temperature measurements.
The suction pressure is determined using a virtual pressure sensor (described in the next section), and suction temperature is measured so [h.
A virtual pressure sensor uses a thermocouple mounted to a return bend of the condenser or evaporator to infer the high-side or low-side pressure.
The most logical explanation for the bias is that the virtual pressure measurement is based on the use of a surface temperature measurement, which is always lower than the refrigerant temperature.