Thermodynamics and heat exchangers

46 CFR §54.01-5

§ 54.01-5 -5 Scope (modifies U-1 and U-2). (a) This part contains requirements for pressure vessels. Table 1 to § 54.01-5 gives a breakdown by parts in this subchapter of the regulations governing various types of pressure vessels, boilers, and thermal units. (b) Pressure vessels are divided into Classes I, I-L (low temperature), II, II-L (low temperature), and III. Table 2 to § 54.01-5 describes these classes and sets out additional requirements for welded pressure vessels. (c) The requirements for pressure vessels by class are as follows: (1) Class I-L and II-L pressure vessels must meet the applicable requirements in this part. (2) Pressure vessels containing hazardous materials as defined in § 150.115 of this chapter must meet the requirements of this part or, as applicable, the r…

46 CFR §56.15-5

§ 56.15-5 -5 Fluid-conditioner fittings. (a) Fluid-conditioner fittings meeting the standards of this part and certified in accordance with subpart 50.25 of this subchapter are acceptable for use in piping systems. (b) Fluid-conditioner fittings made in accordance with the applicable standards listed in table 2 to § 56.60-1 and of materials complying with subpart 56.60 of this part, may be used within the material, size, fluid, pressure, and temperature limitations of those standards and within any further limitations specified in this subchapter. (c) The maximum allowable working pressure may be determined in accordance with § 56.15-1(c). (d) If nonstandard fluid-conditioner fittings are welded, they must be welded in accordance with subpart 56.70 of this part and part 57 of this subc…

DOE-HDBK-1012 §1-1

Temperature, pressure, and energy fundamentals Thermodynamics is the study of energy, its transformations, and its relation to the states of matter. Temperature measures the average kinetic energy of the molecules in a substance and is read on the Fahrenheit and Celsius relative scales or the Rankine and Kelvin absolute scales; absolute zero (0 R, 0 K) is the point of no molecular motion. Absolute temperature must be used in gas-law and cycle calculations. Pressure is force per unit area; gauge pressure is measured relative to atmospheric pressure, while absolute pressure adds atmospheric pressure to gauge (absolute = gauge + atmospheric). A perfect vacuum is zero absolute pressure. Pressures below atmospheric, such as a condenser vacuum, are expressed in inches of mercury vacuum. Energy …

DOE-HDBK-1012 §1-3

First law of thermodynamics and energy balance The first law of thermodynamics is the principle of conservation of energy: energy can be neither created nor destroyed, only converted from one form to another or transferred from one place to another. Applied to a system, it states that the heat added to a system equals the increase in the system's stored energy plus the work the system does on its surroundings. Nothing is ever lost; energy that seems to "disappear" has been converted to a less useful form, most often low-temperature heat rejected to the environment. In practice engineers apply the first law as an energy balance around a piece of equipment or a whole plant: the sum of all energy flows in must equal the sum of all energy flows out plus any change in stored energy. Around a h…

DOE-HDBK-1012 §1-4

Second law, entropy, and efficiency The second law of thermodynamics governs the direction in which energy conversions naturally proceed and sets the ceiling on how much heat can be turned into work. It states that heat flows spontaneously only from a hotter body to a colder one, and that no heat engine can convert all the heat it receives into work — some heat must always be rejected to a lower-temperature sink. This is why every real power plant needs both a heat source (boiler) and a heat sink (condenser/seawater), and why the exhaust and cooling water always carry away energy that cannot be recovered as useful work. Entropy is the property that quantifies the second law; it measures the unavailability of a system's energy to do work, and it always increases in any real (irreversible) …

DOE-HDBK-1012 §1-5

Thermodynamic cycles: Carnot, Rankine, and Diesel A thermodynamic cycle is a series of processes that returns a working fluid to its starting state while converting heat into work, so the cycle can repeat continuously. The Carnot cycle is the ideal reference cycle — two constant-temperature and two frictionless adiabatic processes — and gives the highest efficiency possible between two temperatures, but it cannot be built in practice; it serves as the yardstick against which real cycles are measured. The Rankine cycle is the practical basis of every steam plant. Feedwater is pumped to boiler pressure, the boiler adds heat to make (and superheat) steam, the steam expands through a turbine doing work, and the exhaust is condensed back to water in the condenser, after which the pump returns …