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Energy Basics/Foundation for Understanding
Published in Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo, Energy Conservation Guidebook, 2020
Dale R. Patrick, Stephen W. Fardo, Ray E. Richardson, Brian W. Fardo
The terms heat and temperature are extremely important and must be clarified at this point. Heat is generally described as a measure of quantity, whereas temperature refers to a level of intensity. To distinguish more clearly between these terms, assume that a 5-gallon bucket and a 1-gallon container are filled with water of the same temperature. Water in the bucket will possess much more heat than the container because there are more molecules in it. Heat is directly dependent on both the speed and the number of molecules. A larger volume of water will therefore possess more heat than will a smaller volume. On the other hand, temperature is dependent primarily on the speed with which molecules move. The temperature of a body is therefore determined by the average kinetic energy developed by each molecule. Heat is quite different because it is determined by the total kinetic energy of the molecules. Temperature is measured in degrees with a thermometer, whereas heat is measured in British thermal units (Btu).
Definitions and Terminology
Published in Frank Vignola, Joseph Michalsky, Thomas Stoffel, Solar and Infrared Radiation Measurements, 2019
Frank Vignola, Joseph Michalsky, Thomas Stoffel
Conduction is the transfer of heat through a material as a result of molecular motion. The more heat applied to a material, the faster the molecules that make up the material will vibrate. When heat is applied to a material, the molecules where the heat is applied will vibrate faster. This vibration causes molecules nearest this heat source to vibrate faster, and slowly this vibration spreads throughout the material. For a slab, the rate of heat transfer depends on the area where the heat is applied, the type and structure of the material, the temperature difference across the material, and the thickness of the material. A general formula for heat transfer across a slab is given by () dQdt=−kAdTdx
Pulmonary Changes Induced by the Administration of Carbon Monoxide and Other Compounds In Smoke
Published in David G. Penney, Carbon Monoxide, 2019
Daniel L. Traber, Darien W. Bradford
Direct thermal injury has been shown to cause edema leading to obstruction of the airway above the trachea (Luce et al., 1976; Mellins and Park, 1975; Peters, 1981). Injury from thermal burns below the larynx is extremely uncommon. Mucosal injury generally occurs at air temperatures above 150°C (Crapo, 1984; Herndon et al., 1987; Wald and Balmes, 1990). Heat is energy that is transferred as a result of a temperature difference. Heat energy always flows from a warmer body (higher temperature) to a colder body (lower temperature), until they reach the same temperature. Heat capacity is defined as the quantity of heat necessary to raise a gram of substance 1°C (Weast, 1984). Hot dry air has the heat capacity of about 0.24 cal/g/°C compared to water 1.0 cal/g/°C. Consequently, because of the low heat capacity, even very hot smoke is usually cooled to near 40°C by the time it passes the airway (Moritz et al., 1945). Steam has a heat capacity of 0.48 cal/g/°C, twice that of dry air, but the potential for injury is much higher with steam because as it condenses to water it gives off a considerable amount of calories. Inhalation of steam is a serious burn that is almost universally lethal.
A practical approach-based technical review on effective utilization of exhaust waste heat from combustion engines
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Rajesh Ravi, Oumaima Douadi, Manoranjitham Ezhilchandran, Mustapha Faqir, Elhachmi Essadiqi, Merouan Belkasmi, Shivaprasad K. Vijayalakshmi
In heat exchangers, heat transfer occurs through convection in each fluid while conduction across the separating wall (Amir, Miller, and Jouhara 2017). The heat transfer process can involve latent heat associated with phase changes such as evaporation and condensation or else sensible heat that results from the temperature changes without a phase transition (Arabaci, İ̇çingür, and Emre Arabaci & Yakup Içingür 2016). Heat transfer takes place due to temperature differences, thus transferring heat from one body to another or one part of a body to another (Sharifi et al. 2018). Table 4 summarizes the research conducted earlier on heat exchangers used in WHR systems. Heat exchangers have a broad spectrum of technical applications and household contexts (Guo, Zhang, and Smith 2015). The initial design of a heat exchanger is complex, involving more than just heat transfer analysis (Desideri et al. 2016). The final design must consider various factors such as the installation size, manufacturing feasibility, weight, and the overall cost incurred by the owner (Bahrami, Pourfayaz, and Kasaeian 2022). Even though cost is considered as a crucial factor, the size and footprint often take precedence during the design selection process (Di Battista et al. 2021;).
2-D FEM thermomechanical coupling in the analysis of a flexible eRoad subjected to thermal and traffic loading
Published in Road Materials and Pavement Design, 2023
Talita De Freitas Alves, Thomas Gabet, Rosângela Motta
Assuming that there is no heat sources and sinks, the net heat fluxes must be equal to the storage rate of thermal energy: Where is the density of the material, in kg/m3; is the specific heat capacity, in J/(kg⋅°C); and is the partial derivative of the temperature with respect to time. The specific heat capacity is defined by the amount of heat required to cause a change in temperature by 1°C of a unit of mass of the material. Finally, the Fourier's partial differential equation is the simple balance of and , that must be satisfied in every point x for every moment :
Construction, testing and performance analysis of a multi-stage traveling-wave thermo-acoustic generator
Published in International Journal of Green Energy, 2023
Miniyenkosi Ngcukayitobi, Lagouge Tartibu
In practice, heat is transferred to the system via a hot fluid such as hot water or thermal oil in most thermo-acoustic devices (Abduljalil 2012; Dhuchakallaya and Saechan 2017). In this experimental investigation, electrical heaters were chosen to supply the required heat. These cartridge heaters are constructed to slot easily into drill holes, and have the following specifications: 10mm 150mm, 200W, 220AC. The amount of heat was adjusted through a VARIAC (variable and adjustable voltage transformer). Each engine stage has four cartridge heaters connected in parallel at one side of the regenerator (see Figure 2). Heat is transferred to the regenerator by conduction through copper strips. The conduction process refers to the transfer of heat from a hotter to colder part of an object by direct molecular contact (Arun and Nagaraja 2015; Book 2014). Between the regenerator and the heat exchangers, a number of holes have been drilled to accommodate thermocouples used for temperature measurement. The maximum operating temperature for the hot heat exchanger is between 650 and 1000. Copper strips have been selected because of their high thermal conductivity properties. The machining process and the layout of the HHX arrangement are shown in Figures 2 and 3.