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The Heat Transfer Coefficient (HTC) is defined by the following equation:
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\frac{1}{ r_{ti} \, U} = \frac{1}{r_{ti} \, U_{ti}} + \frac{1}{r_{ti} \, U_t} + \frac{1}{d_{ann} \, U_{ann}} + \frac{1}{r_{ci} \, U_c} + \frac{1}{r_c \, U_{cem}} |
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| outer radius of tubing | ||||
| inner radius of the tubing | ||||
| tubing wall thickness | ||||
| outer radius of casing | ||||
| inner radius of the casing | ||||
| casing wall thickness | ||||
| wellbore radius by drilling bit | ||||
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| Tubing Wall Conductive Heat Transfer Coefficient | ||||
| Annular Flow Heat Transfer Coefficient | ||||
| Casing Wall Conductive Heat Transfer Coefficient | ||||
| Cement Conductive Heat Transfer Coefficient | ||||
| annular hydraulic diameter | ||||
| thermal conductivity of fluid moving through the tubing | ||||
| thermal conductivity of fluid in the annulus | ||||
| thermal conductivity of tubing material | ||||
| thermal conductivity of casing material | ||||
| thermal conductivity of cement |
The equation
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\frac{1}{ r_{ti} \, U} = \frac{2}{\lambda \, {\rm Nu}_{ti}} + \frac{1}{\lambda_t} \, \ln \frac{r_t}{r_{ti}} + \frac{1}{\lambda_{ann} \, {\rm Nu}_{ann}} + \frac{1}{\lambda_c} \ln \frac{r_c}{r_{ci}} + \frac{1}{\lambda_{cem}} \ln \frac{r_w}{r_c} |
where
| effective thermal conductivity of the annulus | ||||
| Natural Convection Heat Transfer Multiplier |
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