Downhole Measurements of Thermal Conductivity in Geothermal Reservoirs

The line source method of determining thermal conductivity is extended to include the transient effect associated with the fluid in flowing geothermal wells. The general equations describing transient heat flow are utilized. Approximate solutions are derived and compared to the exact solution of the general equations. The proposed method is operationally simple since the heater, and the associated problems of obtaining adequate thermal contact between the heater and the sides of the borehole are eliminated. Using this method downhole measurements were obtained and favorably compared with laboratory measurements on characterized core specimens taken from wells in a hot dry rock geothermal reservoir.

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Thermal conductivity of frozen soils

Canadian Journal of Earth Sciences ◽

10.1139/e70-091 ◽

1970 ◽

Vol 7 (3) ◽

pp. 982-987 ◽

Cited By ~ 47

Author(s):

E. Penner

Keyword(s):

Thermal Conductivity ◽

Heat Flow ◽

Silty Clay ◽

Conductivity Measurements ◽

Thermal Probe ◽

Frozen Soils ◽

Transient Heat Flow ◽

Leda Clay ◽

Ice Content

Thermal conductivity measurements of two frozen soils, Leda clay and Sudbury silty clay, taken at temperatures between 0 and −22 °C by means of a thermal probe and a transient heat flow technique, compare favorably with estimates of thermal conductivity calculated by the DeVries method. Both measured and estimated values show a similar trend of increasing thermal conductivity as the temperature is lowered and the ice content grows. This increase is associated with the higher thermal conductivity of ice compared with that of water.

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Measurements of Effective Thermal Conductivity of Azuki Beans by Transient Heat Flow Method Using a Probe.

Nippon Shokuhin Kagaku Kogaku Kaishi ◽

10.3136/nskkk.42.93 ◽

1995 ◽

Vol 42 (2) ◽

pp. 93-99 ◽

Cited By ~ 1

Author(s):

Akio TAGAWA ◽

Satoshi MURATA ◽

Hideaki HINOSAWA

Keyword(s):

Thermal Conductivity ◽

Heat Flow ◽

Effective Thermal Conductivity ◽

Flow Method ◽

Transient Heat Flow

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Reverse Heat Flow with Peltier-Induced Thermoinductive Effect

10.21203/rs.3.rs-369861/v1 ◽

2021 ◽

Author(s):

Kenjiro Okawa ◽

Yasutaka Amagai ◽

Hiroyuki Fujiki ◽

Nobu-Hisa Kaneko

Keyword(s):

Thermal Conductivity ◽

Exact Solution ◽

Solid State ◽

Heat Flow ◽

Negative Temperature ◽

Peltier Effect ◽

Local Cooling ◽

Heating And Cooling ◽

Inductive Component ◽

Ac Current

Abstract The inductive component is the only missing components in thermal circuits unlike their electromagnetic counterparts. Herein, we report an electrically controllable reverse heat flow, which can be regarded as a proper equivalent of the “thermoinductive” effect. The underlying concept is the heating and cooling of the ends of the material by the Peltier effect under an applied ac current; this form a negative temperature gradient in the opposite direction in a controllable manner. We have derived the exact solution indicating that this reverse heat flow occurs universally in solid-state systems, even in conventional metallic Cu, and that it is considerably enhanced by thermoelectric properties (i.e., a large Seebeck coefficient and low thermal conductivity). A local cooling of 25 mK was demonstrated in (Bi,Sb)2Te3, which was explained by our exact solution. This electrically controlled reverse heat flow is directly applicable to the fabrication of a “thermoinductor” in thermal circuits.

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Thermal Conductivity of Selected Ceramic Materials at a Transient Heat Flow

Journal of Applied Materials Engineering ◽

10.35995/jame60010001 ◽

2020 ◽

Vol 60 (1) ◽

pp. 3-11

Author(s):

Jerzy Zych ◽

Janusz Wróbel ◽

Jan Mocek ◽

Marcin Myszka

Keyword(s):

Thermal Conductivity ◽

Heat Flow ◽

Heating Surface ◽

Sample Surface ◽

Ceramic Materials ◽

Heating Process ◽

Heating Rates ◽

Large Steel ◽

Transient Heat Flow ◽

Steel Castings

In this paper, we present comparative investigations. We examined two kinds of ceramic materials used to produce bricks for isothermal cleading of the riser heads of middle and large steel castings. The ceramic materials were characterised by a low specific density (No. 1 − ρ = 0.854 g/cm3; No. 2 − ρ = 0.712 g/cm3). Thermal conductivity tests at a transient heat flow were performed by analysing the heating process of samples taken from the tested ceramic bricks, placed in a special mould in which metal was poured, and by recording the cooling process of the casting. The method proposed in this paper for the determination of samples’ thermo-physical properties is based on measuring the temperature field of the casting–sample system by means of thermocouples situated in various measuring points; it allows the direct investigation of cooling and solidification processes of metals in sand moulds. The heating process of the ceramic samples was analysed by measuring the temperature in five points situated at various distances from the heating surface (casting–sample surface). A large difference in the heating rates of samples of different materials was revealed in our comparative investigations, which indirectly indicated the materials’ heat abstraction ability from the casting surface. The ceramic material characterised by a lower density much slowly conducted heat and, therefore, appeared to be a better material for insulation cleading. At the depth of 40.0 mm, we measured differences in the heating degree corresponding to more than 190 °C. The aim of this comparative study was the evaluation of the suitability of porous insulating materials as cleading of riser heads used in the production of large steel castings.

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