Effect of degree of saturation on thermal conductivity of CLSM used for a horizontal ground coupled heat pump system

摘要

The aim of this paper is to investigate the effect of degree of saturation on thermal conductivityrnof coal ash based CLSM for an use as backfill material of a Horizontal Ground Coupled Heat Pump systemrn(HGCHP). Initially, a family of coal ash based CLSM mixtures with a variable range of water to binder (W/B)rnand water to solid (W/S) ratios, different kinds of binders (e.g., cement and Cementless Binder (CB)) werernsystematically tested in accordance with applicable ASTM Standards to determine general properties of CLSMrnincluding bleeding, flowability, fresh unit weight, initial setting time, and unconfined compressive strength.rnSubsequently, thermal conductivity was measured by using thermal needle probe conforming ASTM D 5334 atrnvarious degrees of saturation ofCLSMspecimens.As a result, the general engineering properties of coal ash basedrnCLSM satisfied the specification ofACI 229R. In addition, a sensitive relationship between degree of saturationrnand thermal conductivity of prepared CLSM mixtures was achieved, the higher the degree of saturation, thernhigher the thermal conductivity. This finding is very important when determining a proper thermal conductivityrnwith respect to various degrees of saturation to play a significant role in achieving optimum performance andrnfull potential toward the use of the given CLSM mixtures as a backfill for trenches of HGCHP. Finally, a thermalrnconductivity prediction equation was proposed as a function of degree of saturation, thermal conductivity underrnfully saturated and dry states.