| Abstract |
TEST OF THERMAL RESPONSE IN SITE OF A HORIZONTAL SERPENTIN SAN LUIS ARGENTINA Engineer Stefanini ValentIn Antonio The objective is to describe a Thermal Response Test (TRT) in situ, obtaining values of the effective thermal conductivity of the subsoil λeff, and the thermal resistance of the borehole of Rb, corresponding to a horizontal system of particular heat exchanger, made in San Luis Argentina. This in situ test was based on the model of the infinite line source (ILS), and the solution to it was made by the graphical method of the slope, which uses the expression of the evolution of the average temperature of the working fluid, as a function of the time (t) and the borehole radius (r), around a linear heat source of constant power (Q) that can be assumed equal to the power of the BHE. Therefore, the thermal conductivity (λeff) is determined based on the slope (k) depending linearly on the medium temperature of the fluid as a function of the natural logarithm of time. (Kun Sang Lee, 2013). The investigation determined the subsoil characteristics, not registered in the region, of the asymmetric horizontal coil, from the model for symmetric vertical exchangers (Eklof C, Gehlin S., 1996). TEST An excavation for swimming pool (4.5 x 2.3 x 1.5) meters was used. On the 7.5 cm concrete floor, an effective 23.36 m long serpentine was placed PEAD diameter ¾ inch K6 pipe suitable for water, holding it to a metal mesh and filling it with a 7.5 cm layer of concrete without additives. An insulated expansion tank is placed with a solution of 100 litters of water with two litters of glycol, electrical resistance, circulation pump and measuring instruments. The test begins on 04/19/2013 without thermal disturbance, determining the undisturbed subsoil temperature, Tsur = 21.65 ºC. On 04/20/2013, the (TRT) began with disturbance. With a duration of 73 hours, culminating on 04/23/2013. The data collection was done manually every 10 minutes, with 818.9 watts of average power, 0.00042 (m3 / sec) of circulating flow. The data is loaded into a spreadsheet and processed. Time criterion, 9 hours, starting point for evaluating the average temperature of the fluid according to the natural logarithm of time. Obtained the value of λeff, we calculate the thermal resistance of the borehole Rb (ºK / (W / m)). RESULTS TRT SAN LUIS ARGENTINA Criterion time Total, Slope 1,97, λeff 1,42(W/m*ºK), Rb 0,117(K / (W/m)) Criterion time 9 hs, Slope 2,28, λeff 1,23(W/m*ºK), Rb 0,087(K / (W/m)) CONCLUSION The λeff, obtained is the reflection of the proposed asymmetric system. How correct is it? Then it was compared visually with respect to TRT worldwide, observing very similar results. Applying a fast and economical method for the evaluation of unconventional exchangers, we obtain acceptable results for a commercial enterprise. That is to say, it is not the same to start from laboratory parameters, then those obtained from a TRT in situ. Keywords: TRT, horizontal exchanger, pending method. |