Heat Transfer Loop Research Articles

Measurement of temperature noise in an out-of-pile heat transfer loop

Temperature noise, or fluctuation in an out-of-pile heat transfer loop was measured and analyzed. Air passed through a round heated steel pipe of 30·0 mm i.d. with Reynolds numbers 2·5 × 10 4 and 5·0 × 10 4. The fluctuating temperature of the air was measured by a fast response thermocouple in the thermal entrance region as well as in the thermally developed region at a number of radial positions. Power spectral density, autocorrelation function, amplitude distribution and the profile of the temperature fluctuation across the flow channel have been measured. Power spectral density, plotted in terms of the local wave number was almost identical for different runs. Assumption of alternating random telegraph signal for the fluctuating temperature gave a measure of hot and cold lumps.

Cross-conduction errors in thermocouples. Correction of long swaged thermocouples at high temperatures

The error due to leakage current flowing through the electrical insulation between the wires of a thermocouple is calculated. The error is due to IR drop along the thermocouple wires, and increases rapidly with temperature and length, and with closeness of contact between the wires and solid insulation. Thus, temperature measurements by swaged sheathed thermocouples in large, high-temperature, liquid-metal and gas-cooled nuclear reactors and heat transfer loops are particularly susceptible. Charts giving the error in the temperature measurements are presented for step and ramp temperature distributions along unsheathed thermocouples, and along sheathed thermocouples with either a grounded or an ungrounded hot junction. Calculation of the correction is illustrated by a typical installation.

Heat Transfer in Sodium—Potassium Alloy

To provide heat transfer data of high precision for NaK heat exchange systems, a NaK heat transfer loop was designed to minimize experimental errors and yield results with a high degree of reproduc...

Local Pressure Gradients in Forced Convection Vaporization

An experimental study of pressure drop in forced convection vaporization has been made in a heat transfer loop designed for the investigation of local heat transfer coefficients and local pressure gradients for water flowing vertically upward in an electrically heated tube. Data presented are for ⅛-in. i.d. 347 stainless steel tubes of 15 and 20-in. lengths with mass fluxes of 200 to 700 lb/sec ft2, heat fluxes of 1 to 8 × 105 Btu/hr-ft2, qualities at the exit up to 50% and with pressures ranging from 50 to 400 psia. A correlation of the local pressure gradients as a function of the Martinelli parameter Xtt has been obtained to within ±15% and a design procedure for calculating over-all pressure drop from this correlation is suggested.

Electric heating and cooking: P. W. Gumaer. ( Scientific American, vol. cxiii, No. 23, December 4, 1915)

The error due to leakage current flowing through the electrical insulation between the wires of a thermocouple is calculated. The error is due to IR drop along the thermocouple wires, and increases rapidly with temperature and length, and with closeness of contact between the wires and solid insulation. Thus, temperature measurements by swaged sheathed thermocouples in large, high-temperature, liquid-metal and gas-cooled nuclear reactors and heat transfer loops are particularly susceptible. Charts giving the error in the temperature measurements are presented for step and ramp temperature distributions along unsheathed thermocouples, and along sheathed thermocouples with either a grounded or an ungrounded hot junction. Calculation of the correction is illustrated by a typical installation.