Question

Determine the height of the chimney to get net draught of 12mm if the total losses are 4mm. the temperature of air is 25^oC and the temperature of chimney gases is 300^oC. The mass of air used per kg of fuel used is 18kg. One kg of air occupies a volume of 0.7734m^3 at normal temperature?

(a) 26.84

(b) 20.22

(c) 29.93

(d) 18.09

I have been asked this question in an online quiz.

I want to ask this question from Draught System topic in chapter Steam Generators & Accessories of Energy Engineering

Answer 1

The correct answer is (c) 29.93

Explanation: Density of air at normal temperature = 1/0.7734

                                           = 1.293Kg/m^3

          Density of air at 298K, ρa = 1.293 × 273/298

                                                        = 1.1845 Kg/m^3

           Density of gases at 573K, ρg = 1.293 × ((18+1)/18) × 273/573

         = 0.65 Kg/m^3

     But, P = 12 + 4

                 = 16 mm of water

                                                  P = H (ρa – ρg)

                                                  16 = H (1.1845 – 0.65)

                                                  H = 29.93m