Radiant Heat

Floor radiant heating systems transfer heat energy from hot water through the floor surface into the room. Traditional systems use a dry-bulb temperature (DBT) sensor mounted on the wall, which measures only the dry-bulb temperature in its immediate vicinity. This measurement controls the temperature and flow rate of the heating water for the entire room. However, this method often results in energy inefficiencies and excessive heating, as it fails to consider the radiant heat and thermal storage of the surrounding surfaces.In response to these energy challenges, this study proposes a Mean Radiant Temperature (MRT) sensing control method and evaluates its energy performance concerning wall emissivity (wall color). An experimental study was conducted to compare MRT sensing control with Dry Bulb Temperature (DBT) sensing control under conditions of black (low emissivity) and reflective (high emissivity) walls. The experimental results were analyzed based on the time required to reach the set-point temperature, floor temperature, and energy consumption.The findings indicate that Mean Radiant Temperature (MRT) sensing control, which takes into account heat storage and the radiant heat of walls, leads to a reduced set-point temperature arrival time and lower energy consumption compared to Dry Bulb Temperature (DBT) sensing control. This effect is particularly pronounced in environments with low-emissivity black walls. These results suggest that MRT sensing control can significantly mitigate energy inefficiencies and reduce excessive heating, thereby contributing to more sustainable and efficient building heating systems.

This paper discusses the merits and deficiencies of some existing and proposed test methods for the evaluation of fabrics intended for protection against radiant heat and flame. Modifications to improve the apparatus and the procedures are suggested. The factors investigated include (1) the means used to obtain a given radiant or convective heat flux; (2) the type, design, and construction of the heat sensor; and (3) the specimen mounting. Standard Test Methods British Standard for Clothing for Protection Against Intense Heat for Short Periods (BS 3791), ISO Test for Evaluation of Thermal Behaviour of Materials and Materials When Exposed to a Source of Radiant Heat (ISO 6942-1981) and ASTM Test for Thermal Protective Performance of Materials for Clothing by Open-Flame Method (D 4108-82) are considered, together with the radiant heat test method proposed in the Federal Aviation Administration's Proposed Flammability Standard for Commercial Transport Flight Attendant Uniforms (FAA-RD-75-176).

This paper investigates the application of recycled steel powder as an additive in concrete to increase the thermal properties of radiant floor heating systems. The project aimed to increase the efficiencies of thermal conductivities, allowing radiant heat to produce higher energy-efficient outputs for heating. Thermocouple readings measured lower temperatures with similar heating conditions as a standard mix slab due to heat transfer occurring evenly through a large surface area, thus transferring heat to the air at faster rates. The tests were completed by casting two 400 × 400 × 200 mm (width × length × depth) slabs enclosing radiant heating pipes. Water was pumped at 40 and 60°C through the pipes. The temperature was recorded at various positions throughout the slab that would allow the multi-layered cylinder approach to analyse the rate of heat transfer, and calculate the efficiency of the heat transfer. The crushing strength of the proposed mix using steel powder replacement is shown to be reduced by 26% when a mix with 12.4% of steel powder is used. Contrary to the original hypothesis of this research, the investigation found rates of heat transfer during the heating stage were 3% lower for the mix containing steel powder compared to the standard mix.

Evaluation and comparison of thermal comfort of convective and radiant heating terminals in office buildings

Correlated two‐photon imaging, also known as “ghost” imaging, has attracted much attention and debate in recent years. The earliest experiments were performed with entangled light, and later with quasi‐thermal light. Our group was the first to use true thermal (incoherent) light to demonstrate two‐photon imaging and interference. We successfully realized lensless ghost imaging with true thermal light at 692.9 nm from the buffer gas in a hollow cathode lamp. The object was a mask with two pinholes separated by 3.66 mm. Furthermore, we analytically studied the effects of higher‐order intensity fluctuation correlations on high‐order ghost imaging and interference, and found that visibility can, in theory, approach the maximum value of 1 as the order increases to infinity. Our experiments on lensless high‐order ghost imaging with a quasithermal light source for orders up to 10 demonstrate that visibility does indeed improve dramatically as the order increases. It is thus possible that high‐order lensless ghost imaging with thermal light may find useful application where conventional imaging techniques are impractical or impossible to use.

The purpose of this study was to quantify the thermal microclimate provided by a shade structure in the African elephant enclosure at Zoo Atlanta. The hypothesis was that the interior of a weather instrument shelter (a Stevenson screen) would provide the maximum environmental shielding and the coolest possible ambient conditions without artificial heating or cooling. The ambient conditions inside the Stevenson screen were compared with the ambient conditions in the shaded and nonshaded sections of the exhibit to quantify the extremes possible under the environmental conditions. The Stevenson screen reduced the radiant heat load by 766 W m−2. The shade structure in the elephant enclosure reduced the radiant heat load by 278 W m−2, which was 37% of the total possible reduction represented by the interior of the Stevenson screen. The longwave radiant heat was 10% greater in the direct sun and 37% greater in the shaded area than the shortwave radiant heat. The shade structure reduced the shortwave radiant heat by 254 W m−2 or 43%, but only reduced the longwave radiant heat by 24Wm−2 or 3%. Shade structures alone may not provide adequate protection from radiant heat for captive species. A cool microclimate in an artificial enclosure should be designed to reduce all sources of radiant heat. Zoo Biol 22:253–260, 2003. © 2003 Wiley‐Liss, Inc.

Perspired moisture plays a crucial role in the thermal physiology and protection of the human body wearing thermal protective clothing. Until now, the role of continuous sweating on heat transfer, when simultaneously considering internal and external heat sources, has not been well-investigated. To bridge this gap, a sweating torso manikin with 12 thermal protective fabric systems and a radiant heat panel were applied to mimic firefighting. The results demonstrated how the effect of radiant heat on heat dissipation interacted with amount of perspired moisture and material properties. A dual effect of perspired moisture was demonstrated. For hydrophilic materials, sweating induced evaporative cooling but also increased radiant heat gain. For hydrophilic station uniforms, the increment of radiant heat gain due to perspired moisture was about 11% of the increase of heat dissipation. On the other hand, perspired moisture can increase evaporative cooling and decrease radiant heat gain for hydrophobic materials. In addition to fabric thermal resistance ( Rct) and evaporative resistance ( Ret), material hydrophilicity and hydrophobicity, emissivity and thickness are important when assessing metabolic heat dissipation and radiant heat gain with profuse sweating under radiant heat. The results provide experimental evidence that Rct and Ret, the general indicators of the clothing thermo-physiological effect, have limitations in characterizing thermal comfort and heat strain during active liquid sweating in radiant heat. This paper offers a more complete insight into clothing thermal characteristics and human thermal behaviors under radiant heat, contributing to the accurate evaluation of thermal stress for occupational and general individuals.

The escalating frequency and severity of bushfires in many countries pose a substantial challenge to the safety of residential buildings. Among the most vulnerable elements of a building's exterior envelope during bushfires are its glass windows, which are highly susceptible to intense heat. This vulnerability can result in large openings in the building envelope, allowing embers, radiant heat, and flames to penetrate the building envelope. This study embarked on a series of fire tests to assess the performance of various window shutters constructed from thin steel sheets, ceramic fibre blankets, and some composites. These shutters were tested under simulated bushfire conditions, including radiant heat, direct flames, and a combination of both. The radiant heat tests adhered to specific curves, simulating varying intensity over 11 and 47 min periods, while the flame zone exposure tests followed the CSIRO/NASH Curve for 47 min. The research findings show that shutters made of steel sheets, or a combination of steel and insulating materials effectively withstand radiant heat and direct flame exposures. They also highlight the superior performance of aluminium foil-backed thin flexible blankets in radiant heat tests. The aluminium foil served as an efficient reflective barrier, redirecting radiant heat towards the fire side. This mechanism significantly lowered the ambient side temperature, maintaining glass temperatures below 50°C in prolonged tests (47 min). The study demonstrates the effectiveness of fire tested window shutters in preventing flame penetration and blocking radiant heat. Enhancing the bushfire resistance of windows offers a crucial layer of protection, substantially increasing the safety of communities in bushfire-prone areas. This research contributes significantly towards developing practical and effective measures for safeguarding houses against the devastating impact of bushfires.

A pilot scale radiant wall oven (RWO) was used to bake potato strips at 12 different time-temperature combinations within 16 min at 290°C to 6.5 min at 365°C. Radiant and overall heat transfer coefficients were experimentally determined for each RWO treatment by monitoring temperature and heat flux. Correlation between heat transfer parameters and quality of the samples was also determined. It was determined that 92%–94% of the overall heat transfer coefficient was contributed by radiant heat transfer. While no correlation was found between color of the RWO baked potato strips and heat transfer coefficients, texture of the RWO baked potato strips was negatively correlated with overall and radiant heat transfer coefficients. Radiant heating could be used as a surface treatment to bake potato strips to mimic the surface of fried strips without increasing their fat content.

The effect of fabric moisture on thermal insulation properties of twelve heat resistant fabrics made with polybenzimidazole (PBI), aromatic polyamide (aramid) and blends of PBI with aramid or with flame retardant rayon fibers is investigated in several high intensity radiant and convective heat exposures. Three fabric preparations were evaluated: oven dry samples, samples condi tioned in a standard atmosphere (65% R.H., 21 ° C) and samples soaked with liquid water. This research shows that moisture enhances the thermal in sulation of all single layer protective fabrics evaluated against 2.0 cal/cm2 ·sec mixed convective exposure and against 0.48 cal/cm2 · sec radiant energy expo sure. Moisture hurts the thermal protective performance (TPP) of the same fabrics in high intensity radiant tests (i.e., 2.0 cal/cm2 · sec, 100% radiant heat). The mechanisms by which moisture acts to change the TPP of a fabric is discussed in light of fabric heating rates.

IMPERIAL CHEMICAL INDUSTRIES, LTD., has recently issued a handy twenty-page booklet on this subject for the purpose of providing information on the properties of radiant heat, to indicate how these apply to the different types of plant now available for stoving paints, and how the qualities of the paints used are affected by the process. The chapter contents of the booklet relate to heat transfer, radiant heat, methods of drying paint, radiant heating equipment, radiant heating technique, and paints and radiant heat. Copies of the booklet may be obtained, free of charge, from I.C.I., Ltd., Belmont, The Ridgeway, Mill Hill, London, N.W.7.

The aims of the present work were to investigate the relationships between radiant heat load, air velocity and body temperatures with or without coincidental exercise to determine the physiological mechanisms that drive thermal comfort and thermoregulatory behaviour. Seven male volunteers wearing swimming trunks in 18°C, 22°C or 26°C air were exposed to increasing air velocities up to 3ms−1 and self-adjusted the intensity of the direct radiant heat received on the front of the body to just maintain overall thermal comfort, at rest or when cycling (60W, 60rpm). During the 30min of the experiments, skin and rectal temperatures were continuously recorded. We hypothesized that mean body temperature should be maintained stable and the intensity of the radiant heat and the mean skin temperatures would be lower when cycling. In all conditions, mean body temperature was lower when facing winds of 3ms−1 than during the first 5min, without wind. When facing winds, in all but the 26°C air, the radiant heat was statistically higher at rest than when exercising. In 26°C air mean skin temperature was lower at rest than when exercising. No other significant difference was observed. In all air temperatures, high correlation coefficients were observed between the air velocity and the radiant heat load. Other factors that we did not measure may have contributed to the constant overall thermal comfort status despite dropping mean skin and body temperatures. It is suggested that the allowance to behaviourally adjust the thermal environment increases the tolerance of cold discomfort.

Devastating large outdoor fires have been responsible for the destruction of vast amounts of infrastructure and the loss of human life. Wildland fires that spread into urban areas, known as wildland-urban interface (WUI) fires, are capable of enormous destruction. WUI fires are distinct from wildland fires; WUI fires include the combustion of both vegetative and human-made fuels and occur where population centers exist, whereas wildland fires include the combustion of vegetative fuels and occur in uninhabited areas. The rise of densely populated urban areas has also seen the development of large urban fires. In addition, the rise of informal settlement communities in Southeast Asia and Africa continues to result in large outdoor fires capable of great destruction. As a wildland fire reaches an urban area, structure-to-structure fire spread processes will occur via the same mechanisms as those in informal settlement fires and urban fires: radiant heat, direct flame contact, and firebrands. Firebrands are in fact the main culprit to destroy structures in large outdoor fires. An additional complication is related to the showers of firebrands produced in large outdoor fires from vegetative and structural fuel combustion, and in the presence of the combustion of these fuel types, there is also radiant heat produced that may only enhance ignition processes. These combined ignition processes have been overlooked and are the subject of this experimental investigation. To this end, a custom experimental apparatus that produces firebrand showers, in the presence of applied radiant heat, was installed inside a wind facility. The firebrand generator was tuned to produce firebrands typical of those quantified from the combustion of structures and the coupled influences of firebrand showers and radiant heat, under various wind speeds was determined. The total firebrand mass for smoldering ignition (SI) decreased as the wind speed and preheating time increased. In all experiments, SI was observed to transition to flaming ignition (FI). To better understand the experimental observations, a simple model was developed and is presented.

We report the demonstration of a second-order interference experiment by use of thermal light emitted from a warm atomic ensemble in two spatially separated unbalanced Michelson interferometers (UMIs). This novel multipath correlation interference with thermal light has been theoretically proposed by Tamma [New J. Phys. 18, 032002 (2016)NJOPFM1367-263010.1088/1367-2630/18/3/032002]. In our experiment, the bright thermal light used for second-order interference is superradiantly emitted via collective two-photon coherence in Doppler-broadened cascade-type Rb 87 atoms. Owing to the long coherence time of the thermal light from the atomic ensemble, we observe its second-order interference in the two independent UMIs by means of time-resolved coincidence detection. The temporal waveforms of the interfering thermal light in the two spatially separated UMIs exhibit similarities with the temporal two-photon waveform of time–energy entangled photon pairs in Franson interferometry. Our results can contribute toward a better understanding of the relation between first- and second-order interferences that are at the heart of photonics-based quantum information science.

In practical thermal light ghost imaging, the nonuniform intensity distribution of the thermal light applied causes distortion of the retrieved image. We propose uniformly weighted arithmetics, including uniformly weighted ghost imaging and uniformly weighted differential ghost imaging (UWDGI), to improve the imaging quality of ghost imaging with nonuniform thermal light fields. Two kinds of nonuniform thermal light fields are discussed, including planar Gaussian distributed thermal light and near-field three-dimensional thermal light. The retrieved image using a uniformly weighted arithmetic has a lower distortion than that using the corresponding traditional ghost imaging arithmetic. In addition, the best imaging quality is achieved with the UWDGI arithmetic.