Català · Español · English

Manen Perez Norbert

Perfil Sortida

Atenea 6.1 ► Els meus cursos ► 2013/14-02:EET-320016-CUTotal ► Tema 5 ► Qüestionari Tema 5 (TANCAMENT: 25 de maig, 23.55 hores)

Qüestionari Tema 5 (TANCAMENT: 25 de maig, 23.55 ho res)

Pregunta 1No s'ha respostencara

Puntuat sobre 1,00

Marca lapregunta

Pregunta 2No s'ha respostencara

Puntuat sobre 1,00

Marca lapregunta

Pregunta 3No s'ha respostencara

Puntuat sobre 1,00

Marca lapregunta

A steam power plant operates between the boiler pressure of 125 bar and the condenserpressure of 0.1 bar. The steam is superheated to 700ºC in the boiler and then expands in theturbine. At the exit from the turbine, the steam is an equilibrium mixture of liquid and vapourwith a quality of 0.887, and it then condenses to saturated liquid in the condenser. Thecondenser is cooled by a mass flow rate of 218 kg/s of cooling water (which may beassumed to have a specific heat capacity of 4.18 kJ/kg·K), which experiences a temperaturerise of 28ºC. The condensed water is then pumped to the pressure of the boiler; it may beassumed that the water is incompressible in this process. Determine the following, giving allthe results to 3 significant figures:

(a) the isentropic efficiency of the turbine, expressed as a percentage %;

(b) the mass flow rate of steam in the cycle, in units of kg/s kg/s;

(c) the power developed by the turbine, in units of MW MW;

(d) the rate of heat absorption in the boiler, in units of MW MW;

(e) the thermal efficiency of the cycle, expressed as a percentage %.

In this question, you need to use the cycle and Figure in Problem 5.3 of the collection ofProblems, but with some small modifications. The cycle is as follows:The steam enters the HP turbine at 20 MPa and 475ºC (state 1), and expands to saturatedvapour at 4 MPa (state 2). A fraction y passes to the FWH, the rest being reheated, withoutloss of pressure, to the same temperature as in state 1. The reheated steam expands in theLP turbine to saturated vapour at 0.005 MPa, and then condenses to saturated liquid at thesame pressure. The total mass flow rate of steam in the cycle is 1200 Mg/h and the fractiony is 25%.

Calculate the following:

(a) the isentropic efficiency of the HP turbine, expressed as a percentage to 1 decimal%;

(b) the rate of heat rejection in the condenser, in units of MW MW;

(c) the total power developed by the two turbines, in units of MW MW.

The fraction y of steam that is extracted from the exit of the HP turbine passes to the FWHwhere it condenses to saturated liquid, exchanging heat with the water emerging from pumpP1, before passing to the pump P2 where the pressure is raised to that of state 1. It is thenmixed with the water from pump P1 and passed to the boiler to close the cycle.

Assuming that the liquid is incompressible and using the approximation dh = v dp for theenthalpy changes in the two pumps, calculate the following:

(d) the specific enthalpy of the mixture at entry to the boiler, in units of kJ/kg and with aprecision of 1 decimal kJ/kg;

(e) the thermal efficiency of the cycle, expressed as a percentage, with a precision of 1decimal %.

An ideal Rankine cycles operates with a boiler pressure of 20 bar, a condenser pressure of0.03 bar and superheat to 450ºC. If the turbine is isentropic, what is the quality of the steamat the turbine exit? Give the result to 3 decimals.

Resposta:

Navegació pel qüestionari

Acaba l'intent ...

1 2 3

Qüestionari Tema 5 (TANCAMENT: 25 de maig, 23.55 hores) http://atenea.upc.edu/moodle/mod/quiz/attempt.php?attempt=611095

1 de 2 17/05/2014 19:10

Atenea és un web accessible.

© UPC. Universitat Politècnica de Catalunya · BarcelonaTech[83] <70/1>

Qüestionari Tema 5 (TANCAMENT: 25 de maig, 23.55 hores) http://atenea.upc.edu/moodle/mod/quiz/attempt.php?attempt=611095

2 de 2 17/05/2014 19:10