A Hybrid Method for Measuring Heat Flux

Hubble, David; Diller, Thomas E.

doi:10.1115/1.4000051

Cited by 27 publications

(13 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The average sensitivity of the ten heat flux sensors on the THeTA is 223 µV (W cm −2 ) −1 with a 95 % time response of 509 ms. The Hybrid Heat Flux (HHF) (Hubble & Diller 2010a) technique was used to improve the initial time response of the THeTA. The HHF is a numerical signal processing technique which increases the performance of differential heat flux sensors by accounting for the thermal energy stored within the sensor in conjunction with the heat flowing through the sensor.…”

Section: Water Tunnel Facility and Turbulence Generationmentioning

confidence: 99%

The role of large-scale vortical structures in transient convective heat transfer augmentation

2013

Self Cite

View full text Add to dashboard Cite

The physical mechanism by which large-scale vortical structures augment convective heat transfer is a fundamental problem of turbulent flows. To investigate this phenomenon, two separate experiments were performed using simultaneous heat transfer and flow field measurements to study the vortex-wall interaction. Individual vortices were identified and studied both as part of a turbulent stagnation flow and as isolated vortex rings impacting on a surface. By examining the temporal evolution of both the flow field and the resulting heat transfer, it was observed that the surface thermal transport was governed by the transient interaction of the vortical structure with the wall. The magnitude of the heat transfer augmentation was dependent on the instantaneous strength, size and position of the vortex relative to the boundary layer. Based on these observations, an analytical model was developed from first principles that predicts the time-resolved surface convection using the transient properties of the vortical structure during its interaction with the wall. The analytical model was then applied, first to the simplified vortex ring model and then to the more complex stagnation region experiments. In both cases, the model was able to accurately predict the time-resolved convection resulting from the vortex interactions with the wall. These results reveal the central role of large-scale turbulent structures in the augmentation of thermal transport and establish a simple model for quantitative predictions of transient heat transfer.

show abstract

Section: Water Tunnel Facility and Turbulence Generationmentioning

confidence: 99%

The role of large-scale vortical structures in transient convective heat transfer augmentation

2013

Self Cite

View full text Add to dashboard Cite

show abstract

“…A new algorithm has recently been proposed by Hubble and Diller [34] to markedly improve the response time of heat flux measurements using a differential sensor architecture. This hybrid heat flux model uses the sensor both as a differential and calorimeter (slug) heat flux sensor.…”

Section: B Transient Response Under Ambient Conditionsmentioning

confidence: 99%

“…This hybrid heat flux model uses the sensor both as a differential and calorimeter (slug) heat flux sensor. The sensor initially behaves like a calorimeter at short time scales, but as time increases, the behavior transitions to a differential-based mechanism [34]. The hybrid heat flux model requires the output from the thermopile as well as individual temperature measurements from both the bottom and top thermocouple layers.…”

Section: B Transient Response Under Ambient Conditionsmentioning

confidence: 99%

See 1 more Smart Citation

High-Temperature Calibration of Direct Write Heat Flux Sensors From 25 °C to 860 °C Using the In-Cavity Radiation Method

et al. 2015

Self Cite

View full text Add to dashboard Cite

Heat flux sensors fabricated using Direct Write Thermal Spray are thin, surface-based devices that can operate at high temperatures. In this paper, Direct Write heat flux sensors are calibrated over a temperature range of 25°C-860°C. A substitution-based quartz lamp configuration is used to measure the steady-state sensitivity and transient response of Direct Write sensors at ambient temperatures, with repeatability confirmed over a 10-month period and after thermal aging. A matched heat flow approach is used to characterize the sensors at operating temperatures up to 860°C. The sensitivity is found to increase by a factor of two from 25°C to 650°C, after which it plateaus up to the maximum tested temperature of 860°C. A cubic polynomial calibration function captures the temperature dependence of the sensitivity and provides a good agreement for the measured data.Index Terms-Heat flux, heat flux sensor, high temperature, thermal sensor, heat flow sensor, thermopile.

show abstract

“…Unfortunately, there are many situations where this is not possible, particularly in fire testing. Recently, a simple method has been developed specifically to deal with this issue [24]. It uses a hybrid method for obtaining the net heat flux measurements, q", by combining both thermopile differential heat flux (q" diff ) with the temporal slug calorimeter heat flux (q" slug ).…”

Section: Hybrid Heat Flux Gagementioning

confidence: 99%

Quantifying Thermal Boundary Condition Details Using a Hybrid Heat Flux Gage

Lattimer¹,

Diller²

2011

Fire Safety Science - Proceedings of the 10th International Sym

View full text Add to dashboard Cite

New methods and experimental techniques were developed in this research to quantify the incident heat flux, absorbed (net) heat flux into a sample, and heat transfer coefficient for samples exposed to mixed mode (radiation and convection) heat transfer typical in fires. Net heat flux into the material was measured at elevated temperatures using a recently developed hybrid heat flux gage, which is both a thermopile type gage as well as a slug calorimeter with an operating temperature >1000 ºC without cooling. The heat transfer coefficient was determined as a function of time using the hybrid gage output only through a reference state approach. The net heat flux and heat transfer coefficient were then used to calculate a cold surface heat flux and the adiabatic surface temperature. Experiments were performed in the cone calorimeter at different heat fluxes to quantify the incident heat flux, net heat flux, heat transfer coefficient, cold surface heat flux, and adiabatic surface temperature as a function of time. Measured heat transfer coefficients were 9-18 % different than values calculated using idealized natural convection correlations. The cold surface heat fluxes determined with the hybrid gage were within 5 % of cold surface heat fluxes measured using a water-cooled Schmidt-Boelter heat flux gage.KEYWORDS: heat flux, heat transfer coefficient, adiabatic surface temperature, cone calorimeter, high temperature heat flux gage, hybrid gage. NOMENCLATURE LISTINGA s area of exposed surface (m 2 ) β thermal expansion coefficient (

show abstract

A Hybrid Method for Measuring Heat Flux

Cited by 27 publications

References 15 publications

The role of large-scale vortical structures in transient convective heat transfer augmentation

The role of large-scale vortical structures in transient convective heat transfer augmentation

High-Temperature Calibration of Direct Write Heat Flux Sensors From 25 °C to 860 °C Using the In-Cavity Radiation Method

Quantifying Thermal Boundary Condition Details Using a Hybrid Heat Flux Gage

Contact Info

Product

Resources

About