Net terrestrial radiant flux in the vertical over Pune

The terrestrial radiant fluxes are being measured regularly at Pune using a balloon-borne radiometersonde. The net terrestrial radiant fluxes obtained from these measurements over a decade have been studied and results presented. The net terrestrial radiant flux increases with height and reaches a maximum around 12 km and then the rate of increase slows down near tropopause. In the lower stratosphere the fluxes again Increase before reaching a nearly steady value at around 25 km. The clouds and rainfall distributions seriously distort the radiation field.

Optical Power Scale Realization by Laser Calorimeter after 45 Years of Operation

To calibrate laser power and energy meters, the National Institute of Standards and Technology (NIST) uses several detector-based realizations of the scale for optical radiant flux; these realizations are appropriate for specific laser power/energy ranges and optical coupling configurations. Calibrations from 1 μW to 2 W are currently based upon calorimeters. Validation by comparisons against other primary representations of the optical watt over the last two decades suggests the instruments operate well within their typical reported uncertainty level of 0.86 % with 95 % confidence. The dominant uncertainty contribution in the instrument is attributable to light scattered by the legacy window, which was not previously recognized. The inherent electro-optical inequivalence in the calorimeter’s response was reassessed by thermal modeling to be 0.03 %. The principal contributions to the overall inequivalence were corrected, yielding a shift in scale representation under 0.2 % for typical calibrations. With updates in several uncertainty contributions resulting from this reassessment, the resulting combined expanded uncertainty (k = 2) is 0.84 %, which is essentially unchanged from the previous result provided to calibration customers.

Future Definition of the Candela Based on Single Photons

We discuss the candela (cd), the SI unit for light intensity, and its relation to single-photon technology. Currently, the definition of candela is based on the radiant flux in the unit of watts (W) with a fixed constant Kcd, and its primary standard is implemented electrically. Recent advances in the generation and the detection of a single photon indicate that photon-counting techniques with very small uncertainties of less than 1 ppm will become available in the near future. Thus single-photon technology will allow the light intensity to be defined simply in terms of the number of photons counted rather than the power measured in watts.

A Refinement Of The Determination Method Of The Linear low-pressure Uv Lamps Radiant Flux

For the measurement of linear low-pressure UV lamps radiant flux the method proposed by the IUVA, which is based on the Keitz method, has become widely used. For deriving the equation that connects the irradiance generated by a lamp at a close distance and its radiant flux, the authors of the method presume that the lamp is the cylinder of equal radiance. According to our estimates, this assumption leads to the inaccuracy of 3 % to 5 % with respect to goniophotometric measurements. In this research, a general formula is derived that connects the irradiance generated by a linear emitter and its radiant flux. This formula does not impose restrictions on the radiant intensity curve in the longitudinal plane. The Keitz equation is its particularcase. To reduce the inaccuracy of the IUVA method, the angular distribution of the radiant intensity of the UV lamps is proposed to be approximated by a cosine polynomial. In order to find the coefficients of the polynomial,clarify the Keitz formula, as well as to estimate the inaccuracy of the refined and classical versions of this formula, the series of goniophotometric measurements of the DB15, DB18, DB30 lamps at various distances was carried out. It was found that at a scanning step Δθ = 5° the first 9 terms of the trigonometric expansion are sufficient to describe the radiant intensity curve with accuracy satisfactory for practical use. It was also shown that the Keitz method needs to be refined only on the basis of goniophotometric data obtained upon condition r / l ≥ 6 where r is the test distance, l is the lamp length. It was identified that in the case of a differentiated approach, the approximation of the low-pressure UV lamps radiant intensity curve by a cosine polynomial makes it possible to provide an inaccuracy of simplified methods that does not exceed 1 % in relation to the goniophotometric method. It is in dicated that in order to find a universal factor applicable for the entire range of linear low-pressure UV lamps, the development and the analysis of statistical data is required.

Evaluating Radiant Heater Performance Using Chick Thermal Preference and Spatial Analysis

HighlightsRadiant heaters from different manufacturers with the same power output do not produce the same radiant distribution.Heater net usable area is influenced by heater elevation and chick preferences for radiant flux.Radiant heaters should be operated at manufacturer specified elevations to minimize potential reductions in performance.Abstract. Radiant heaters are the most common method of providing supplemental heat in broiler houses, but little is known about how efficiently they create a suitable thermal environment for brooding chicks. This study investigates the net usable area (NUA), or the total floor area within the range of radiant flux preferred by chicks, for six round radiant heaters with a nominally rated power output of 11.72 kW. NUA was calculated for all heaters at three manufacturer specified heights 1.52, 1.83, and 1.98 m and at a distance 0.3 m below manufacturer specified height (1.22 m). NUA ranged from 11.6 ± 0.7 m2 to 59.4 ± 19.7 m2 and increased with heater mounting elevation. Results indicate that radiant heaters from different manufacturers with the same power output do not produce the same NUA. NUA was also shown to be higher at 8 d than 1 d for all heaters and was attributed to the decrease in chick preference for level of radiant flux during the first week of brooding. NUA gross radiant coefficient (GRC), or the proportion of the heat energy in the fuel that reached the floor and was within the thermal comfort range of the chicks, did not exceed 0.37 for any heater and decreased with heater elevation. Operating a heater below the manufacturer specified mounting elevations led to reduced NUA and an overall less efficient use of fuel. Keywords: Broiler chicks, Brooding, Net usable area, Radiant heaters, Thermal preference.

Construction and Operating Parameters of Adsorptive Chillers

The chapter is devoted to the design and performance of adsorptive chillers. Basic types of design and operating principle of adsorptive chillers were analyzed. Advantages and disadvantages performance of one-, two-, three-, and four-bed solar power adsorptive chillers are compared. Performance of adsorptive refrigerators based on composite adsorbents was studied. The correlation between the adsorbent composition and the coefficient of energy performance of the adsorptive chiler was revealed. An optimal composition of adsorbent 'silica gel – sodium sulphate' is stated to be of 20% silica gel and 80% sodium sulphate. The maximal values of the coefficient of performance of cycle of studied solar adsorptive chiller about of 1.14 are stated for composites containing about 20 wt. % silica gel and 80 wt% sodium sulphate. As a consequence of decreasing of adsorbent mass, the coefficient of performance is shown to increase when sodium sulphate content in the composite increased. Regeneration process parameters of the composite were shown to strongly affect on the coefficient of performance of the adsorptive chiller. The growth of the coefficient of performance is stated to result from decreasing the difference between adsorbent temperature and regeneration temperature from 85 to 55°C. The basic factors affecting the net coefficient of energy performance of the adsorptive solar refrigerator were stated daily solar radiant flux alongside with composition of the adsorbent and difference between adsorbent temperature and temperature regeneration. Net coefficients of performance of solar adsorptive refrigerator based on composite ‘silica gel – sodium sulphate' were stated to change from 0.25 to 0.34 during operating period. Utilization of the adsorption heat is suggested to warm the heat carrier which applied to heat adsorbent during regeneration. The ways to improve the design and performance of adsorptive solar chillers are suggested. The first one involves the introduction of solar collectors made of cellular polycarbonate plastics in the design of adsorptive solar chiller. Instantaneous efficiency coefficient were calculated as special thermal performance-solar radiant flux surface density ratio, optical efficiency factor is determined as special thermal performance-solar radiant flux surface density ratio at the equal temperatures of heat transfer medium and environment, reduced heat loss factor being calculated as the product of solar collector efficiency factor and net heat loss coefficient. The environmental test of developed collectors PSK-AV2-3, PSK-AV1-2, PSK-AV2-1, PSK-VS1-2, PSK-VS2-2, PSK-VS2-3, PSK-ST10-PW were conducted. The correlation of their results with laboratory tests when the thermohydraulic stand applied is shown. Relative accuracy of laboratory and environment tests was shown to be not exceeding 5 – 7%. The optical efficiency factor and the coefficient of thermal losses of polymeric solar collectors were determined. On the basis of the dependencies of the efficiency of the solar collectors vs. the reduced temperature, optimal designs of the polymeric solar collectors for the adsorption chilling solar systems are determined to be depended on the temperature of the regeneration temperature of the sorbents. As the temperatures of the regeneration of composite adsorbent ranged from 50ºС to 60ºС, appliance of the collectors PSK-AV2-1, PSK-CT10-PW occur to be expedient, and PSK-AB2-3, PSK-VS2-3, PSK-AB1-2, PSK-VS2-2, and PSK-VS1-2 are revealed to be more efficient when regeneration temperatures increased over 80 ºС. Thermotechnical characteristics of designed polymeric solar collectors are shown to surpass conventional metal and vacuum collectors. The perspectives of polymeric solar collectors in the design of adsorptive chilling solar plants were shown. Another way to improve the performance of adsorptive solar chillers concerns with equipping it with a photosensitive element and an electric drive, which will allow changing the angle of slope of the adsorber to the horizon depending on the intensity of the solar radiation. The chapter can be useful for design the efficient adsorptive chilling plants.

SIMULATION OF THE RADIANT HEAT TRANSFER PROCESS IN THE ELEMENTS OF ROASTING EQUIPMENT

The object of the research is the process of radiation heat transfer, taking into account a single reflection of rays in the IR device of food production. Investigated problem – the work is devoted to solving the problem of irregularity of radiation heat transfer during infrared roasting of food products. Main scientific results. The inverse problem of heat transfer by radiation has been solved and a technique has been developed for determining the profiles of the ray flux reflectors for uniform irradiation of receivers of a convex section. Analytical modeling of all-round uniform irradiation of an elliptical receiver has been carried out. An experimental device with low-inertia temperature sensors for infrared roasting of semi-finished meat products has been developed, which makes it possible to use a reflector shaped according to the developed analytical technique. The verification of the created technique for determining the profiles of reflectors by means of a computer experiment using the TracePro and Mathcad software systems has been carried out. The area of practical use of the research results: the use of an experimental device with a radiant flux reflector for roasting semi-finished meat products proves that the obtained technique for profiling reflectors of heat engineering systems is acceptable for the design of infrared equipment for food production and restaurant facilities. This technique allows simulating the profile of the radiant flux reflector depending on the shape of the receiver. Studies have shown that the use of a profiled reflector in the experimental device reduces the duration of roasting of natural portioned semi-finished beef products by 33 %. Innovative technological product: a technique for determining the profiles of ray flux reflectors for uniform irradiation of receivers with a convex section. Device for infrared roasting of semi-finished meat products. Scope of application of an innovative technological product. The study of an experimental device with a designed radiant flux reflector for roasting semi-finished meat products proves that the obtained technique for profiling reflectors of heat engineering systems is acceptable for the design of infrared equipment for food production and restaurant facilities. Using this approach allows to approach the solution of the problem of irregularity of irradiation of products during infrared roasting

Modelling and Experimental Investigation of Luminous Coupling in UVLED Driven Optical Fiber Reactors

Background: Photocatalytic oxidation is a promising tool for waste water treatment and decomposition of biologically non digestible substances. Immersed nanoscale catalyst particles from semiconductor materials such as TiO2 and ZnO can be excited by absorbed UV radiation, leading to hydroxyl-ion formation at the surface of the semiconductor and oxidative degradation of pollutants. Objective: This contribution deals with reactors equipped with catalyst coated light guides to combine the advantages of immobilized catalysts with nearly homogeneous irradiation. With experimental and theoretical methods the coupling and decoupling of radiation were investigated and the performance of catalyst coated light guides was tested by means of methylene-blue degradation. Methods: Radiation models, known from the recent literature, use single ray, parallel ray or multi ray models to approximate the light transmission. These models neglect Fresnel reflection and consider only coupling into the light guide. In this study, the LED was simulated as a Lambertian radiator using 10 4 rays with angle dependent intensities. This well-known model was extended with Fresnelreflection, which predicted the measured coupling efficiencies accurately. The simulations predict the decoupling and catalyst activation at the lateral surface of the light guide for two boundary cases, ideal matt and ideal reflective surfaces. To generate matt surfaces, the light guides were either scratched or coated with TiO2 p25 nanopowder. Sol-gel coating methods were used, to create reflective surfaces. Results: When using matt surfaces, the decoupling rate is very high: 80% of the radiant flux exits the light guide in less than 10 cm. If light guides with reflective surfaces are used, the radiant flux leaving the light guide is low: less than 10% of the radiation exited the light conductor in the first 10 cm. Methyleneblue degradation, seen as a model reaction, was used to determine the reactor performance by comparing the pseudo first order reaction coefficients. Due to the uniform light distribution along the length of the light guides and the resulting even formation of reactive radicals, the quantum yield was increased by a factor of 3, using sol-gel coated light guides, rather than powder coated light guides. Conclusion: The effectiveness of LED driven optical fiber reactors was intensified, if reflective surfaces are used instead of matt surfaces. These surfaces are achieved by sol gel chemistry. However, to use the complete amount of photons, which entered the optical fiber, very long light guides are needed.