Thermal Performance Analysis of Hydronic Ceiling Radiant Panel Heaters Under Different Parameters

A numerical analysis of a ceiling type radiant panel heater system was performed to examine the heating performance under different parameters, using the FloEFD code. Three-dimensional models of the room and radiant panel heater were created and the effects of the Reynolds number, water inlet temperature, pipe diameter and pipe runs on the heating performance of the system were examined in detail. The effects of these parameters on the total heat load, the net radiation rate, and the average surface temperature on the sheet and insulation material have been presented. The total heat load and net radiation rate obtained from the system increase with increase in the Reynolds number. Also, a rise in the water inlet temperature increases the heat output of the system. An increase of approximately 500 W was observed in the total heat output as the pipe diameter increased. It was observed, too, that the heat output increased with increase in pipe runs, although above a certain value the heat output became almost constant. The results of this study could offer information to engineers and manufacturers on the design and use of hydronic radiant systems.

Mixed Convection Stagnation Point Flow of a Hybrid Nanofluid Past a Permeable Flat Plate with Radiation Effect

This article focuses on the stagnation point flow of hybrid nanofluid towards a flat plate. The cases when the buoyancy forces and the flow are in the opposite direction and the same direction are discussed. The effect of radiation and suction is also taken into account. The similarity transformations are used to convert the partial differential equations into nonlinear ordinary differential equations. These equations are computed numerically via the bvp4c function in MATLAB software. A comparison with the previously published articles is carried out, where an outstanding agreement is observed. The dual solutions exist in the case of opposing flow (λ<0) and the suction parameter S>0.6688. Meanwhile, only unique solutions exist in the case of assisting flow (λ>0). The existence of dual solutions leads to stability analysis. From the analysis, the first solution is confirmed as a stable solution. Furthermore, the heat transmission rate increases, while the skin friction coefficient decreases as the radiation rate increases. An increase in the radiation rate from 0 (no radiation) to 1.0 increases the heat transmission rate by 5.01% for water, 4.96% for nanofluid, and 4.80% for hybrid nanofluid. Finally, it is worth mentioning that the present study yields new and original results. This study has also not been done by other researchers, indicating its novelty.

Post-Newtonian properties of EMRI with power law potential

There are many astrophysical scenarios where extreme mass ratio inspiral (EMRI) binaries can be surrounded by inhomogenous matter distribution. The distribution of mass can affect the dynamical properties (e.g. orbital frequency, average energy radiation rate, etc.) of the EMRI. In this matter distribution, instead of Kepler–Newton potential, one may consider a more general form of potential i.e. power law potential. Moreover, due to the power law potential, at the Newtonian order itself, the velocity profile of test particles does not fall as much as that predicted by Kepler–Newton potential and this feature of the velocity profile may be observationally important. In this study, we have obtained the first post-Newtonian (1PN) expressions for dynamical quantities and the average energy radiation rate from the circular orbit EMRI which is surrounded by a matter distribution. We show that the energy radiation rate and orbital frequency of EMRI can be significantly different in the presence of power law potential as compared to that in the Kepler–Newton potential, signatures of which may be observed in gravitational waves from EMRI.

Hyperradiance by a stream of phase-correlated atomic dipole pairs traversing a high-Q cavity

Hyperradiance in which radiation rate exceeds that of superradiance has been theoretically investigated in various coherently-coupled emitter-field systems. In most cases, either proposed setups were experimentally challenging or the mean photon number in a cavity was limited. In this paper, with numerical simulations and analytic calculations, we demonstrate that significant hyperradiance with a large mean photon number can occur in a microlaser system, where pairs of two-level atoms prepared in quantum superposition states traverse a high-Q cavity in the presence of a pump field intersecting the cavity mode. Hyperradiance is induced when the intracavity-pump Rabi frequency is out of phase with respect to the atom-cavity coupling so that the reduction of atomic polarization by the atom-cavity coupling is compensated by the pump Rabi frequency in the steady state to maximize atomic photoemission.

Universal lasing condition

Usually, the cavity is considered an intrinsic part of laser design to enable coherent emission. For different types of cavities, it is assumed that the light coherence is achieved by different ways. We show that regardless of the type of cavity, the lasing condition is universal and is determined by the ratio of the width of the atomic spectrum to the product of the number of atoms and the spontaneous radiation rate in the laser structure. We demonstrate that cavity does not play a crucial role in lasing since it merely decreases the threshold by increasing the photon emission rate thanks to the Purcell effect. A threshold reduction can be achieved in a cavity-free structure by tuning the local density of states of the electromagnetic field. This paves the way for the design of laser devices based on cavity-free systems.

Far Infrared Radiation Property of Elbaite/Alumina Composite Materials

Far infrared materials have been prepared by precipitation method using natural elbaite powder as raw materials, which belongs to tourmaline group. The chemical formula of elbaite is Na(Al, Li)3Al6B3Si6O27(O, OH, F)4. X-ray powder diffraction (XRD) shows that elbaite and alumina in composite material has good crystal form. In addition, XRD results indicate the formation of alumina crystallites show that alumina powder exists as nano-meter particles on the surface of elbaite powder. It can be calculated the particles diameter of Al2O3 is 47.86nm. The maximum infrared radiation rate of tourmaline/alumina composite materials is 0.89 when the ratio of alumina in elbaite powder is 20%. The infrared radiation rate has been increased by 0.03, compared with single elbaite. It shows that the infrared radiation rate of the composite materials is higher than any of a single component. Two reasons are attributed to the improve of the rate of far infrared radiation: alumina powder exists as nano-meter particles and different materials will increase the absorption peak and the vibration intensity in FTIR spectra.

Effects of Gamma Radiation on Resonant and Antiresonant Characteristics of Piezoelectric Wafer Active Sensors

This paper presents gamma radiation effects on resonant and antiresonant characteristics of piezoelectric wafer active sensors (PWAS) for structural health monitoring (SHM) applications to nuclear-spent fuel storage facilities. The irradiation test was done in a Co-60 gamma irradiator. Lead zirconate titanate (PZT) and Gallium Orthophosphate (GaPO4) PWAS transducers were exposed to 225 kGy gamma radiation dose. First, 2 kGy of total radiation dose was achieved with slower radiation rate at 0.1 kGy/h for 20; h then the remaining radiation dose was achieved with accelerated radiation rate at 1.233 kGy/h for 192 h. The total cumulative radiation dose of 225 kGy is equivalent to 256 years of operation in nuclear-spent fuel storage facilities. Electro-mechanical impedance and admittance (EMIA) signatures were measured after each gamma radiation exposure. Radiation-dependent logarithmic sensitivity of PZT-PWAS in-plane and thickness modes resonance frequency (∂(fR)/∂( logeRd)) was estimated as 0.244 kHz and 7.44 kHz, respectively; the logarithmic sensitivity of GaPO4-PWAS in-plane and thickness modes resonance frequency was estimated as 0.0629 kHz and 2.454 kHz, respectively. Therefore, GaPO4-PWAS EMIA spectra show more gamma radiation endurance than PZT-PWAS. Scanning electron microscope (SEM) and X-ray diffraction method (XRD) was used to investigate the microstructure and crystal structure of PWAS transducers. From SEM and XRD results, it can be inferred that there is no significant variation in the morphology, the crystal structure, and grain size before and after the irradiation exposure.