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Thermodynamic Cycles

2 tools in the Fluids and Heat Transfer area.

Power and Refrigeration Cycles

State-by-state analysis of the five textbook power and refrigeration cycles. Brayton (gas turbine: pressure ratio, turbine inlet temperature, compressor and turbine isentropic efficiencies, optional regenerator, intercooling and reheat), Otto and Diesel (compression ratio, cutoff ratio, heat added per kilogram or peak temperature) are computed with variable specific heats from the NASA Glenn seven-coefficient fits of McBride, Zehe and Gordon (air, nitrogen, oxygen, argon, carbon dioxide or water vapour) and the cold-air-standard constant-k closed forms are printed beside them. Rankine steam cycles (superheat, reheat, one open feedwater heater, turbine and pump efficiencies) use the IAPWS-IF97 steam properties and the vapour-compression refrigeration cycle (R-134a, ammonia, carbon dioxide or propane; superheat, subcooling, compressor efficiency) the NIST WebBook tables of the shared fluid-property library. Every state is tabulated (p, T, v, h, s, x), every process equation is written with its numbers, and the specific work and heat, net work, thermal efficiency or COP, back-work ratio, mass flow for an entered power or capacity and the Carnot bound are reported with the T-s diagram (saturation dome for the vapour cycles) and the p-v diagram of the gas cycles. Defaults: Brayton with r_p 10, 300 K inlet and 1,400 K turbine inlet, efficiencies 0.85 / 0.90 and a regenerator of effectiveness 0.80 (η 44.8 %, 307 kJ/kg net); Otto r 8 with 1,000 kJ/kg; Diesel r 18, r_c 2; Rankine 8 MPa / 500 °C to 10 kPa with reheat at 1 MPa; R-134a between −10 °C and 40 °C with 5 K superheat and subcooling for 10 kW.

1 worked example reproduced, listed on the tool page.

Steam System and Boiler Efficiency

Boiler efficiency by the heat-loss (indirect) method from the fuel ultimate analysis, the flue-gas oxygen or carbon dioxide and the stack temperature (dry-gas, fuel-moisture and hydrogen, air-moisture, unburned-carbon, carbon-monoxide, radiation and unaccounted losses on the HHV and LHV bases, the combustion stoichiometry computed from the analysis, the direct input-output method when the fuel input is measured), with the five fuel analyses of Army TM 5-650 as selectable defaults and an efficiency chart against stack temperature and excess air. Steam-system balance on IAPWS-IF97 properties: header steam, feedwater, blowdown, condensate and makeup enthalpies, blowdown from cycles of concentration or TDS limits, flash-steam recovery, the deaerator steam demand from its mass and energy balance, economizer and air-preheater savings, fuel input, steam generation per unit fuel, annual fuel cost and the fuel cost of steam in the form of DOE Steam Tip Sheet #15. Steam trap and leak losses by Napier's orifice formula, bare and insulated pipe heat loss by cylindrical conduction with natural convection and radiation at the surface, a backpressure turbine against a pressure-reducing valve (isentropic expansion with an entered efficiency, power per 1,000 lb/h, cost of the generated power from the extra boiler steam), and the blowdown water and chemical arithmetic. Default: an illustrative 50,000 lb/h, 150 psig natural-gas boiler with 3 % flue-gas oxygen and a 450 °F stack.

1 worked example reproduced, listed on the tool page.

Other Fluids and Heat Transfer sections

Pipe Flow · Pumps and Fans · Compressible Flow · Conduction · Convection · Radiation · Heat Exchangers · Fluid Properties