A theoretical model has been created to predict the thermal conductivity of knitted structures in terms of porosity, thickness and moisture content. The validity of the model was examined by the results of experiments conducted using different knitted fabrics, in which the porosity, thickness, fibre and water content are different. The thermal conductivity of a dry plain knitted fabric decreases with the increase of porosity; however, with increased water content, the increase of porosity contributes to an increase in thermal conductivity.

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This paper presents the working principle of a wearable miniature cooling system investigated by us for managing heat and sweat effectively and efficiently under extreme conditions. The cooling system consists of peltier units and mini refrigerant channels incorporated in a knitted spacer structure. The knitted spacer structure absorbs sweat and accumulates it to keep the skin dry. The cold side of the peltier units absorbs heat from the skin and transfer the heat to the refrigerant, which is converted to a gas by the absorption of evaporative heat. The mini refrigerant channels are connected to a high pressure liquid refrigerant cylinder and to a gas receiver via polymer tubes. The wearable cooling system was evaluated by using a test rig designed to simulate the origination of human body heat and a sealed environment similar to that inside a CBRN garment. Test results show that the temperature remains constant, when the cooling system is active even though the heat energy was produced continuously. This wearable cooling system can be used to manage heat and sweat under extreme conditions.

A geometrical model of plain knitted structures is discussed in depth to understand the yarn path in a knitted loop. A theoretical model has been created to predict the porosity of a knitted structure depending on the geometrical parameters, such as course spacing, wale spacing, stitch length, fabric thickness, count of yarn and fibre density. Polyester and nylon plain knitted fabrics were produced to different tightness, and porosity was determined by measuring the weight. The validity of the model was confirmed by experimental results, using different plain knit fabrics. The porosity of a knitted structure can be changed by reducing the yarn thickness and the stitch length; however this would influence the courses and wales per unit length in the structure.

The absorbency properties of knitted structures are very important in designing garments that both remove liquid sweat from the skin and provide tactile and sensorial comfort to the wearer. Water absorbency by knitted spacer structures was experimentally investigated using a gravimetric absorbency tester to record absorbency rate, total absorbency, and time taken to saturate the structure. The geometry of spacer structures was analyzed and a model created to define the capillary characteristic in the spacer yarn.Absorbency into the spacer structures was modeled using the fabric parameters, the capillary radius, and the properties of water. Experimental and theoretical results were compared to validate the models.