PhD Thesis - Energy Systems Research Unit - University of Strathclyde

Fig. 2.34 - Internal heat gains emitted due to occupants2.5.3 Internal heat gains due to appliances2.5.3.1 Electrical appliancesInternal heat gains due to appliances are much more complex to model. Similarly totheir electrical demand different appliances have different heat emission values.However, contrary to electrical loads, which can be considered as instantaneousloads, which go ‘On’ or ‘Off’ instantaneously, heat gains emitted from appliancesshow what is termed a time delay effect [57].An important aspect of appliance related internal heat gains is that appliances wouldcontinue to emit heat even after being switched ‘Off’. Likewise after switching ‘On’,an appliance would take some time to warm up before reaching its steady-stateworking temperature. One presumption which is therefore being made in thismodelling is that both the heating up and cooling down periods are of such a shortduration in comparison to the time the appliance is considered to being emitting heatat its working temperature, that they can be neglected. For appliances whose thermalmass is small (e.g. small electronic equipment etc.), this is a reasonable assumptionas the heat is gained and dissipated quickly. For other appliances such as electricovens this is a coarse approximation which merits further analysis as part of possiblefuture work annexed to this research.Assuming a low thermal inertia, appliance internal heat gains can be modelled in a73