Thermal Responses of the Hand to Convective and Contact Cold : with and without Gloves

Abstract: Many outdoor working tasks and some indoor working tasks still require the worker to perform them in a cold condition. To cope with cold condition, warm clothing is usually applied. Nowadays, the thermal protection of clothing is sufficient but the extremities are still not very well protected. It is very difficult to provide sufficient thermal protection to the hand, that does not decrease the hand performance. In the literature review of this thesis, the most important factors and topics related to the cooling of the hand and fingers are summarized.The issue of cold contact is still not sufficiently studies. How fast the skin may cool down to a dangerous level and how many factors may influence the contact cooling was not clear. There are five empirical studies concerned with cold surface contact by bare and gloved hand which are summarized in the thesis. The experimental studies of contact cooling of the bare finger and gloved finger were carried out in a small climate chamber. Many factors which may possibly influence the contact cooling were considered. These factors include: contact force; surface temperature; material property; surface mass; the thermal situation of the whole body and the morphology of the fingers.For the technical determination of the thermal resistance of the gloves, a mini hot plate was developed according to the EN 511 (36) and ISO 5085 (72) standards. The error from doubledetermination was less than 4%.The skin temperature (Tsk) was the dependent measurement for all of the studies. It varied on the different points of the hand. The measurement points and the location for measuring the Tsk is critical. Tsk and cold induced-vasodilatation showed a very local phenomenon. For unequal cooling (such as contact), the contact Tsk is critical and needs to be considered separately.The results indicated, that a modified Newtonian cooling curve with two time constants provided the best regression function for the contact Tsk of bare hand contact on cold surfaces and it may also be possible to describe the contact Tsk of a gloved hand.