Indoor Thermal Environment in Supermarkets. A study of measured and perceived comfort parameters.

Licentiate thesis, 2009

In the supermarket environment three different groups must be considered: food (food quality), personnel (working conditions) and customers. Customers are of particular interest since they make up the commercial basis for the supermarket. Currently, however, there are no recommendations on the indoor environment for this category. To start a discussion on this topic and to provide a tentative recommendation, this thesis presents a state-of-the-art overview related to different systems and their operation in supermarkets as well as theories for the thermal balance of humans, display cabinets and refrigerated food. Few studies compare the perceived indoor thermal environment in supermarkets based on questionnaires with simultaneous measurements of the thermal environment. In this thesis the findings of such investigations in the cold environment of chilled food display cabinets are discussed. The basic hypothesis is that objective measures can be used in order to estimate the perceived thermal environment sufficiently well, with the following assumptions and limitations: • the comfort equation in ISO 7730 can be used to estimate the perceived thermal comfort (Predicted Mean Vote, PMV), in a supermarket. • the comfort equation can be used outside its verified range in terms of thermal gradients and residence time sufficiently well to prescribe suitable thermal environments for customers and personnel in supermarkets. • the mean temperature at the point of residence is more important for the perceived comfort than the temperature gradient between ankle and head. • questionnaires can be used to evaluate thermal comfort for customers and personnel in a supermarket environment. This work shows that it is possible to use objective measurements in order to estimate the perceived thermal environment in supermarkets, with some limitations. Perceived and predicted PMV have shown systematic interdependence. In summer, however, differences between the measures tend to be larger. For customers, the perceived PMV is lower during the summer. The perception, however, is not as low as the predicted PMV would indicate. One reason is probably that in summer customers are wearing light clothes, light indoor shoes and are more exposed to the cold environment than the case would be in winter. However, customers do not stay very long in this environment and it is not necessary to account for a long exposure time in the cold environment. As a result of this work the thesis proposes some guiding principles for an appropriate thermal environment in chilled food aisles and discusses some ideas for future work.