Thermal Sensation
One of the factors recorded in the qualitative experiments was thermal sensation: this asked our participants to rank how 'warm' or 'cool' they were on a scale from 'cold' to 'hot'. A follow up question asked what their preferred temperature would be, this might seem redundant but actually provides a greater deal of understanding - for instance, it is possible to both feel warm and want to be even warmer. The collated responses are indicated in the following two charts.
To aid in analysing these results, the responses were equated with numerical values. For example, 'Neutral' becomes 0, 'Slightly Warm' becomes 1 and 'Slightly Cool' becomes -1. Using this method, it was possible to calculate an 'average' value for each condition to give a simplified overview to compare cases. These averages are presented in the graph below. In addition to the lines representing the averages, columns have been superimposed to include the preferences from the second chart above.
There are several conclusions that can be drawn from this. Firstly, the final three conditions (the 24°C conditions) result in the participants feeling a noticeable increase in temperature for every air speed. Secondly, the medium fan speed results in the highest perceived thermal sensation for each of the two temperatures, although the effect is much more pronounced in the lower temperature conditions. It is hypothesized that this large difference is in part due to the fact that the first condition tended to receive the 'neutral' response because the participants had not experienced the other conditions and so had nothing but the room to compare against. Another contributing factor to this is that the high speed air is likely to have a 'wind chill' effect on skin, causing the participant to feel slightly cooler even in the same temperatures.
The final thing to note here is that the temperatures used in all of the conditions were deemed 'warm' by the vast majority of the participants, and very few desired an increase in temperature. This would suggest that perhaps a more useful approach would be to include cooling capabilities to the system, as the average preference is for slightly cooler air even at 20°C.