Uppvärmd konstgräsplan : Beräkning av utnyttjningstid för en uppvärmd konstgräplan med alternativa rörplaceringar

Sammanfattning: For Skattkärr IF a turf field with warming has been projected to increase field’s utilization hours and to have a longer period for athletes to perform their activities outdoors. The technique chosen to heat the plan is a type of a geothermal heating system without a heat pump. The brine, which is water with 30% ethanol, collects heat from the borehole and discharges it to a coil in the field. There is at position 11 boreholes but it is planned to increase the number to 31, which is the design for the facility. The operating cost of the system consists of a pump. The heating cables, which are connected in parallel, consist of PVC tube and the total length is about 40 kilometers. The heating cables are 154 mm in plan, with a c/c distance of 200 mm. Forward and return line temperatures are 5.5°C and 2.5°C and the flow is 73m3/h. The purpose of this work is to explore how the placement of coils (laying depth and c/c distance) affect heat transport capability of the plan area, describe the utilization time that can be expected for the football field in Skattkärr and calculate the impact of the heating system on the football field utilization time . The goal of this work is to create a mathematical model using computer programs that describe the surface temperature over a year. For artificial turf pitch to be playable the surface temperature should be at least 0°C. The model whose task was to describe the surface temperature was built in the program Simulink, (a part of Matlab) and consisted of several descriptions of energy flows, amongst others: convection, radiation and evaporation. To describe the heat flow from the pipe to the surface, the program Comsol was used. Various heat transfer coefficients were calculated with different tube placements later used in Simulink. The results show that with the heating system, utilization hours increased from 4200 hours to 4800 hours per year. With a c/c distance of 150 mm and an installation depth of 100 mm, useful hours can be increased by another 400 hours. According to the model, a brine temperature of 40ºC is required to increase the utilization time up to 7000 hours per year, with a calculated electricity consumption of about 262 MWh/year. The sensitivity analysis performed on the material's thermal conductivity shows that the choice of material for similar heating systems is important and affects the heat flow from the pipe to the surface.