Building Heat Loss Research Articles

Review Article.The physical basis of current infrared remote-sensing techniques and the interpretation of data from aerial surveys

Abstract The range of infrared (IR) detectors at present available is described and a comparison is made between their performances with reference to particular applications. Due to the increasing availability and use of IR sensors the problems involved in data interpretation are becoming more widely acknowledged. Hence the major part of this paper is devoted to a detailed survey of these problems and offers a guide to those wishing to use IR data either quantitatively or qualitatively. Throughout, special reference is made to airborne IR surveys and their application to building heat loss.

Growth, properties and applications of HgCdTe

This paper provides primarily a review of the methods used to grow HgCdTe with a summary of some of its basic properties and applications. Methods of crystal growth fall generally into three classes: growth from the melt, from solution and from the vapor phase. All three methods have been and are being used to grow HgCdTe. The high vapor pressure of HgCdTe at the melting point, combined with a large segregation coefficient, have effectively limited the use of Czochralski or zone melting techniques, but two melt growth techniques have survived: (1) a variation of Bridgman growth called quench-anneal wherein a dendritic crystal is formed by quenching the melt and is homogenized by solid state recrystallization below the melting point, (2) a variation of freezing from a large volume called slush-growth wherein a melt is held in a temperature gradient for several weeks while a crystal grows. Growth from solution has taken the form of liquid phase epitaxy (LPE) on CdTe with the LPE systems including growth from Hg-rich, HgTe-rich and Te-rich solutions and using tipping, vertical dipping, vertical sliding and horizontal sliding. Vapor phase growth is very promising but is not yet in production. Techniques include growth by isothermal close spaced epitaxy in which HgTe is transported isothermally by chemical potential onto CdTe, molecular beam epitaxy (MBE) in which elements are evaporated in a high vacuum, and metal organic chemical vapor deposition (MOCVD) in which some of the metal atoms are carried to the substrate bound to organic radicals before being freed by pyrolysis. In all these methods, control of Hg pressure is a major concern. The fundamental properties discussed briefly are those of prime interest to detector manufacturers: energy gap (Eg), intrinsic carrier concentration (ni), and electrical activity of dopants. A reasonable fit to the Eg data from ȣ 20 papers is given by Eg = -0.302+1.93x+5.35×10-4T(1ȡ2x)-0.810x2+0.832x3. This gap, combined with k·p calculations, gives the intrinsic carrier concentration as a function of composition and temperature: ni = (5.585-3.820x+1.753×10-3T-1.364×10-3xT)×1014E3/4gT3/2 exp(-Eg/2kT). HgCdTe is typically used in the manufacture of infrared (IR) detectors, with both commercial applications such as medical thermography and building heat loss analysis and military applications such as surveillance of activities on the surface of the earth and terminal guidance of missiles. Detectors operating in the atmospheric windows are able to see both in the dark and through clouds. HgCdTe is the material of choice for the 3ȁ5 μm and the 8ȁ12 μm wavelength IR detectors. HgCdTe is not strong or easy to work with, but the technology is maturing and sophisticated devices are now being built.

Quantitative Methods In Aerial Thermography

Quantitative methods for measurement of absolute (kinetic) surface temperatures of roof surfaces from aerial thermal data are discussed. Methods of accounting for atmospheric variation, background reflectance, path radiance, and roof emissivity effects are also discussed. The quantitative method has been tested in several research programs under the sponsorship of the New York State Energy Research and Development Authority and the U.S. Depart-ment of Energy. The results of these tests, which are presented here, represent a comparison of concurrent contact and aerial roof temperature measurements on a variety of roof surfaces. These tests indicate that kinetic roof surface temperatures can be measured from wholly airborne data with a standard error of 1.0°C. The implications of these results for airborne measurement of building heat loss are presented in this paper.

A comparison of two procedures for optimum sizing of a solar heating system

A model for building heat loss that includes hourly variation in solar radiation and windspeed was designed for use in evaluating solar heating system performance. Numerical simulations were run to see if, from an economic standpoint, the two effects were sufficiently large that a different solar collector size would be chosen than that selected using a heat loss model incorporating temperature only. The results show that solar system performance for the two models is significantly different on a daily basis but similar on a long term basis due to compensating factors. Thus, the simple model is adequate for selecting the optimum size of a solar collector.

Infrared Scanner Technology Applied to Building Heat Loss Determination

Infrared Scanner Technology Applied to Building Heat Loss Determination

Computer Simulation of Fuel Requirements for Growing Broilers

ABSTRACT SINCE the energy crisis of 1973, the Delmarva Poultry Industry has been faced with rapidly increasing fuel costs as well as an uncertain fuel supply. To assist the Delmarva Poultry Industry in minimizing fuel costs and developing conservation measures, a computer simulation study was in-itiated to investigate the effect of broiler house construction features and grower management practices on the supplemental heat energy (LP gas) required for brooding chicks. The mathematical description of the broiler house, the broiler and the interaction with management prac-tices was divided into two programs; (a) broiler house heat loss and (b) broiler house heat balance. The out-put from the building heat loss pro-gram is used as an input to the heat balance program. Since the inception of the study, the Delmarva grower companies have used the programs to evaluate proposed changes in house construction and management prac-tices before implementation in the field.