Radiant Coefficients Research Articles

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.

Comparing Radiant Heater Performance Using Spatial Modeling

Abstract. Radiant heaters are the preferred method of providing supplemental heat in poultry houses because they heat the floor and chicks directly to create a suitable microclimate by allowing for a range of thermal comfort options. Heat distribution at the floor is commonly evaluated using infrared thermography, which provides assessments of floor temperature distributions but cannot directly compare energy reaching the floor to energy consumed. The objectives of this study were to develop a system to measure the radiant energy emitted by round radiant heaters that reached the floor (measuring plane), use spatial modeling to estimate total radiant flux output at the measuring plane, and compare heater gross radiant coefficients (GRC). A radiant heater test stand was constructed over a set of linear arrays mounted with thin-film radiant flux sensors. Radiant flux measurements (n=160 per heater) were taken within the heated area of six round radiant heaters with a nominal rated output of 11.72 kW. Radiant flux data were collected at heater canopy elevations of 1.22, 1.52, 1.83, and 1.98 m above the measuring plane. Results from non-linear regression analysis showed that for all heater and elevation combinations, the radial distance from the heater center axis to 95% of the final asymptotic value was 4.71 m or less. Total heated area ranged from 13.90 to 61.46 m2 between 1.22 and 1.83 m canopy elevations. Mean radiant energy reaching the measuring plane was 2.54, 3.00, 3.34, and 4.29 kW for canopy elevations of 1.22, 1.52, 1.83, and 1.98 m, respectively. Mean gross heat input was 10.76 kW and ranged from 9.39 to 13.17 kW across all heaters. GRC ranged from 0.21 to 0.41 and increased with heater elevations. Keywords: Brooding, Gross radiant coefficient, Heater performance, Radiant flux, Radiant heating.

Performance Analysis on Improvement of the Heat Insulation of Grain Storehouse

There is about 80 percent heat passing from roof into storehouse. A contrastive test is carried through on improvement of the heat insulation of grain storehouse’s roof, adopting aluminum foil with large reflection coefficient and low radiant coefficient and hard-forth urethane with low heat transfer coefficient. The result indicates both of the two materials have a better effect, especially combination with them. It can not only decrease 4～5°C in storehouses and 3～4°C in grains at the highest temperature, but also delay aging of grain. However the aluminum foil will crack in more than two years. It shows superiority both in effect and natural life, according to the test which is conducted using sun proof paint as substitute for aluminum foil. The conclusion is that it is a preferable technical measure of improvement of the heat insulation to sprinkle paint of heat insulation and sun proof and forth urethane on roof of storehouses built.

Water turbidity estimation using a hand‐held spectropolarimeter to determine surface reflection polarization in visible, near and short‐wave infrared bands

This letter describes a radiometric technique to evaluate the turbidity (suspended solids concentration, SSC) of terrestrial waters (e.g. irrigation canals, creeks, ponds, streams and small rivers) using a hand‐held spectropolarimeter. A field experiment was conducted using a container of water with different turbidity levels. The intensity and degree of polarization of sunlight reflected from the water were measured in visible, near and short‐wave infrared bands. The intensity of the reflected light and its non‐polarized component were divided by the incident sunlight intensity to derive the radiant coefficient (Q, %), and the non‐polarized radiant coefficient (Qnp, %), respectively. The Q and Qnp in several wavelength bands were regressed against measured values of SSC. The multiple regression model using multi‐band Qnp is superior to a similar model using multi‐band Q because the Qnp model does not need viewing angles as explanatory variables, whereas the model using Q requires these angles. A result from preliminary testing in real streams is also presented.