Hasil untuk "Heat"

S. Whitaker

J. Sclater, C. Jaupart, D. Galson

Per Eskilson

J. Reddy, D. Gartling

W. Qu, I. Mudawar

Yiping Dai, Jiangfeng Wang, Lin Gao

Changying Zhao, W. Lu, Yuan Tian

Weerapun Duangthongsuk, S. Wongwises

J. Larkindale, J. D. Hall, M. Knight et al.

R. Dole, M. Hoerling, J. Perlwitz et al.

Neil Zuckerman, N. Lior

E. Ouhabaz

M. Mashaly, G. Hendricks, M. Kalama et al.

The present study was conducted to determine the adverse effects of high temperature and humidity not only on live performance and egg quality but also on immune function in commercial laying hens. One hundred eighty 31-wk-old laying hens at peak production were used in this study. Hens were housed in cages (15 cages of 4 birds/cage) in each of 3 environmental chambers and received 1 of 3 treatments. The 3 treatments were control (average temperature and relative humidity), cyclic (daily cyclic temperature and humidity), and heat stress (constant heat and humidity) for 5 wk. Different production and immune parameters were measured. Body weight and feed consumption were significantly reduced in hens in the heat stress group. Egg production, egg weight, shell weight, shell thickness, and specific gravity were significantly inhibited among hens in the heat stress group. Likewise, total white blood cell (WBC) counts and antibody production were significantly inhibited in hens in the heat stress group. In addition, mortality was higher in the heat stress group compared to the cyclic and control groups. Even though T- and B-lymphocyte activities were not significantly affected by any of the treatments, lymphocytes from hens in the heat stress group had the least activity at 1 wk following treatment. These results indicate that heat stress not only adversely affects production performance but also inhibits immune function.

Lin Liu, Yuanzhi Zhang

In this paper, the effect of urban heat island is analyzed using the Landsat TM data and ASTER data in 2005 as a case study in Hong Kong. Two algorithms were applied to retrieve the land surface temperature (LST) distribution from the Landsat TM and ASTER data. The spatial pattern of LST in the study area is retrieved to characterize their local effects on urban heat island. In addition, the correlation between LST and the normalized difference vegetation index (NDVI), the normalized difference build-up index (NDBI) is analyzed to explore the impacts of the green land and the build-up land on the urban heat island by calculating the ecological evaluation index of sub-urban areas. The results indicate that the effect of urban heat island in Hong Kong is mainly located in three sub-urban areas, namely, Kowloon Island, the northern Hong Kong Island and Hong Kong International Airport. The correlation between LST and NDVI, NDBI also indicates that the negative correlation of LST and NDVI suggests that the green land can weaken the effect on urban heat island, while the positive correlation between LST and NDBI means that the built-up land can strengthen the effect of urban heat island in our case study. Although satellite data (e.g., Landsat TM and ASTER thermal bands data) can be applied to examine the distribution of urban heat islands in places such as Hong Kong, the method still needs to be refined with in situ measurements of LST in future studies.

R. Schittny, M. Kadic, S. Guenneau et al.

It was recently shown theoretically that the time-dependent heat conduction equation is form invariant under curvilinear coordinate transformations. Thus, in analogy to transformation optics, fictitious transformed space can be mapped onto (meta)materials with spatially inhomogeneous and anisotropic heat-conductivity tensors in the laboratory space. On this basis, we design, fabricate, and characterize a microstructured thermal cloak that molds the flow of heat around an object in a metal plate. This allows for transient protection of the object from heating while maintaining the same downstream heat flow as without object and cloak.

A. Betz, J. Jenkins, C. Kim et al.

Abstract With recent advances in micro- and nanofabrication, superhydrophilic and superhydrophobic surfaces have been developed. The statics and dynamics of fluids on these surfaces have been well characterized. However, few investigations have been made into the potential of these surfaces to control and enhance other transport phenomena. In this article, we characterize pool boiling on surfaces with wettabilities varied from superhydrophobic to superhydrophilic, and provide nucleation measurements. The most interesting result of our measurements is that the largest heat transfer coefficients are reached not on surfaces with spatially uniform wettability, but on biphilic surfaces, which juxtapose hydrophilic and hydrophobic regions. We develop an analytical model that describes how biphilic surfaces effectively manage the vapor and liquid transport, delaying critical heat flux and maximizing the heat transfer coefficient. Finally, we manufacture and test the first superbiphilic surfaces (juxtaposing superhydrophobic and superhydrophilic regions), which show exceptional performance in pool boiling, combining high critical heat fluxes over 100 W/cm2 with very high heat transfer coefficients, over 100 kW/m2K.

G. Huminic, A. Huminic

Zhonghao Rao, Shuangfeng Wang, Maochun Wu et al.

Romaissa Fillali, Boudjemaa Agoudjil, Nawal Chennouf et al.

This study investigates the thermal performance and heat transfer mechanisms of a wall constructed with Hollow Date Palm fiber Concrete Blocks (HDPCB) through combined experimental and numerical analyses. Steady state and dynamic laboratory measurements were conducted to determine the wall's thermal transmittance, thermal resistance, time lag, decrement factor, and periodic thermal transmittance. A 3D model was developed to simulate heat transfer through the solid components of the wall and natural convection within the cavities, while the contribution of radiative heat transfer was evaluated separately. Sensitivity analysis was performed to identify the factor with the greatest influence on predicted heat transfer. Experimental results indicate that HDPCB walls provide effective thermal insulation, with a U value of 1.23 W m−2 K−1 and an R value of 0.81 m2 K W−1. Numerical predictions agreed with measurements within 3%, confirming that natural convection is the dominant heat transfer mode within the cavities of the blocks under the tested conditions. These results demonstrate the potential of HDPCB as a sustainable and energy-efficient building envelope solution.