Heat flux sensor pdf

Heat flux is the flow of thermal energy per unit area. Heat flux is the amount of thermal energy that is moving through a material while temperature is more of a measure of the amount of thermal energy contained at a certain point. Most heat flux sensors that are available on the market are differential-temperature thermopiles. They operate by creating a relatively small temperature difference across a thermal resistance layer TRL which is the core material of the heat flux sensor.

Using Fourier's law of heat conduction with a one-dimensional heat transfer assumption under steady-state conditions, the temperature difference across the TRL is proportional to the heat flux through the sensor shown in the equation below and diagram to the right. Where q" is the heat flux, k is the thermal conductivity of the sensors, d is the thickness of the sensor, and T is the temperatures on the top and bottom surfaces of the sensor.

Thermopile based heat flux sensors utilize thermoelectric elements that form thermocouple junctions on either side of the thermal resistance layer.

The thermocouple junction pairs induce an analog DC voltage that is actually directly proportional to the temperature difference. This is much easier than accurately measuring each surface temperature individually. Multiple thermocouple junction pairs are placed in electrical series so that the output analog DC voltage from the heat flux sensor is amplified to increase overall sensitivity of the sensor.

Calibrating the heat flux sensors can then relate this output voltage signal directly to the heat flux that is flowing through the sensor using a sensor sensitivity value that is provided with every heat flux sensor from FluxTeq. Heat flux is a valuable measurement to make in a wide variety of applications.

While temperature typically can only tell you about the current state of a thermal system, heat flux can be used to predict the future behavior of a system. FluxTeq's PHFS heat flux sensor product line is specified to endure temperatures within the range of to degrees Celsius to degrees Fahrenheit.

Heat flux sensors, similar to thermocouples, output an analog DC voltage signal that has been calibrated to directly correlate to the amount of heat flux that is flowing through the sensor.

Each sensor is provided with a sensitivity constant value that is used to make this conversion calculation. Typically these voltages can be relatively small in the microVolt range so it is necessary to have some sort of precision voltmeter or data acquisition device that can resolve these signals. FluxTeq recommends using a device that is capable of resolving around 1 microVolt in order to get accurate measurements from the heat flux sensors. FluxTeq has the unique capability of manufacturing custom sized heat flux sensors for your application.

The first section only considered the highest outside temperature reached during the experiment. The second section, in contrast, looked at the lowest outside temperature reached during the experiment. Each section focused on the specified hours and the walls that showed good results for all the days of the experiment. Thus, the results, for most of the days of the experiment, were somewhat repeated.

This will be presented in the following sections, especially when the weather was clear, that is, no rain or clouds. For a better idea of the results, a full day of data recording was selected for each section. This was a sample representing the average temperatures of all the inside sensors during the specified hours.

Highest Outside Temperature The ambient temperature of all chambers increased from 7 a. On some days, the peak was reached at 1 p. Figure 6 shows that the 14th of February , as a sample day, presented the average of outside and inside sensors for each chamber.

Figure 7 shows only some of the hours 11 a. The sample day, 14th of February , showed that both PCMs reached both phases melting and solidifying at the outside ambient temperatures, Tout. Tout represented the average of outside sensors for the sample day: started at a.

About 7. Both figures show that the two PCMs performed better in absorbing heat and keeping the chambers in thermal comfort during the peak time than the foam and hollow bricks alone. Bearing in mind the average of all days for inside surface sensors, PCM RT35 absorbed more heat and provided better cooling than all chambers for the north wall only. At the peak time for indoor sensors , or 1 p. Taking 14 February as an example, at 12 p. Figure Figure 6.

Sample Sample day, which was day, which was the the 14th 14th of of February February Figure 7. Figure The north 7. The north wall wall of of all all chambers chambers that that showed showed the the coolest coolest inside inside temperature. For the reference chamber, it was Both PCMs gave good results in general, that is, better cooling.

Then, it started to reduce until a. Lowest Outside Temperature Reached This part focuses on the lowest ambient temperature of all chambers from the peak time, with a stable gradient, to reach the lowest temperature at 6 a.

Figure 8 shows the results of 19 December as a sample day that showed the average of all outside and inside surface sensors for each chamber. The lowest Tout was recorded by the roof sensors of each chamber for an ambient temperature between This figures showedemphasized the benefits that the PCMs of chambers kept the PCMs as effective warmer materials usedor than the foam in buildings, the especially in regions such as the Middle East.

Figure 8. Sample day, which was the 19th of December To discuss this result in detail, first let us take a close look at 19 December as an example. Figure 8 shows the lowest temperature during the day at 6 a.

Second, both PCMs showed better performance than in the previous part. Specifically, both PCMs were able to preserve more heat in winter than they could absorb heat in summer. Sustainability , 13, 12 of 17 Figure 8. Figure 9. The ceiling of all chambers that showed the warmest temperature. As an additional step in the study, the average temperature of the entire walls of the 4. For the sample day, the result showed the This part following: the presents referencethe calculated chamber resultsa.

On chamber, This emphasized the benefits of PCMs as effective materials used in buildings, especially in regions such as the Middle East. Rate of Heat Transfer and Heat Flux Based on The Collected Data This part presents the calculated results based on the assumptions described in the Methodology section, with an uncertainty Equation 5 of Moreover, the rate of heat transfer and the heat flux focused only on the bricks and heat that flowed between their surfaces.

Figures 10 and 11 show the rate of heat transfer and the heat flux during the sample day when the hottest temperature was reached, and Figures 12 and 13 show the same for all the days. The negative sign in all the figures represents the heat flow direction when the outside temperature was higher than the inside.

Figures 10 and 11 show that both the rate of heat transfer and the heat flux of RT35 showed a greater reduction in heat transfer at — h and — h. For instance, the heat flux for the RT35 chamber at 12 a.

For instance, the heat flux for the RT35 chamber at 12 Sustainability , 13, 13 of 17 a. Figure Therate The rateofofheat heattransfer transfer for for the the 14th 14th of of February February Figure Theheat The heatflux fluxfor forthe thesample sample day day during during the the hottest hottesttemperature temperatureoutside. Sustainability , 13, 14 of 17 Figure The heat flux for the sample day during the hottest temperature outside.

The rateof ofheat heattransfer transfer for the north wall. The heat flux flux for the north north wall. PCM 4. Yet, the PCMs showed effectiveness in reducing energy consumption more than the polystyrene foam and brick alone, which can be for the long term. The PCM bag used in the experiment weighed approximately 3 kg, and each wall of the chamber contained one hollow brick, except the ceiling.

Research Limitations This experiment had some limitations that should be noted: 1. The experiment studied the performance of insulation in only one location, which is inside hollow bricks.

This experiment was just a small prototype to investigate PCMs as a building material and to study their thermal performance. The initial cost and energy consumption cost for the same materials used in the experiment can possibly be investigated in future research on an actual scale.

The experiment chambers were fully closed, with no opening for ventilation to study the PCM behavior. The chambers were designed to be small due to the limited amount of PCMs and the affordability of their price. The experiment did not study the possibility of leakage when the PCMs reached the melting phase and became liquid.

All the noted limitations will be considered in future research by the authors. Conclusions This study was an experiment conducted to investigate the effect of the thermal behaviors of two types of PCM that have different melting ranges and compare it with that of polystyrene foam. To accomplish this experiment, we decided to study four chambers built from hollow bricks. One of them was kept empty as a reference, and each of the remaining chambers had the cavity inside filled with different types of insulation placed on the four walls and ceiling.

Sustainability , 13, 16 of 17 Based on the assumptions indicated in the methodology, PCM RT35 showed a greater reduction in the heat flux by However, the PCMs indicated efficiency in decreasing energy consumption more than polystyrene foam and bricks, which possibly might be for the long term. This experiment is simply a small example of exploring and studying PCMs as effective building materials and investigating their thermal performance.

The primary cost and energy consumption cost for the equivalent materials used in practice can probably be studied in future research on an actual scale. However, this study initiated a relevant window of opportunity for additional experiments to determine the interrelatedness of the suggested uses of phase change materials PCMs with the assistance of empirical studies.

The phase change material PCM applications have strong experimental support and are creating greater demands for additional empirical studies to discuss the PCM applications more evidently. Excitingly, the literature reveals that the uses of PCMs retain the same importance and can be discussed in developing and developed countries. It is recommended to use phase change materials and undertake more research to reduce heat gain and energy consumption in hot and humid climate countries, such as Saudi Arabia.

Thus, the implications for energy consumption management and for future research on the uses of phase change materials were noted. Author Contributions: A. All authors have read and agreed to the published version of the manuscript.

Funding: This research received no external funding. Institutional Review Board Statement: Not applicable. Informed Consent Statement: Not applicable. Data Availability Statement: Not applicable. Conflicts of Interest: The authors declare no conflict of interest. References 1. Conti, J. Al-Saadi, S. Performance-based envelope design for residential buildings in hot climates.

Meteorology, National Center for Meteorology. KSA Climate. Saudi Electricity Company. General Authority for Statistics. Costanzo, V. The effectiveness of phase change materials in relation to summer thermal comfort in air-conditioned office buildings. Rathore, P. Potential of macroencapsulated PCM for thermal energy storage in buildings: A comprehensive review. Zhou, D. Review on thermal energy storage with phase change materials PCMs in building applications.

Energy , 92, — Ben-Abdallah, R. Experimental investigation of the use of PCM in an open display cabinet for energy management purposes. Energy Convers. Navarro, L. Thermal energy storage in building integrated thermal systems: A review. Part 1. Active storage systems. Energy , 88, — Part 2. Integration as passive system. Energy , 85, — Vicente, R. Brick masonry walls with PCM macrocapsules: An experimental approach.

Abu-Hamdeh, N. Energy Technol. Chen, X. Optimization and sensitivity analysis of design parameters for a ventilation system using phase change materials. Li, Y. Investigation on the energy performance of using air-source heat pump to charge PCM storage tank. Energy Storage , 28, Memon, S. Phase change materials integrated in building walls: A state of the art review. Energy Rev. Feldman, D.

Obtaining an energy storing building material by direct incorporation of an organic phase change material in gypsum wallboard. Energy Mater. Konuklu, Y. Review on using microencapsulated phase change materials PCM in building applications.