Question

Problem Statement: Design a tubular feed-water heater which need to heat the 1.5 kg/s of water from 20°C to 60°C. Constraints: a) Heating of water need to be done by saturated steam which is condensing at 1 MPa & heat transfer coefficients (on steam side) is 6500 W/m²K b) Max. Velocity of water 1.0 m/s c) Three different copper tube inner diameters 2.0 cm, 2.5 cm and 3.0 cm. d) Thickness of copper tubes 10% of the inner diameter Deliverables: 1. You need to provide the solution for the given problem statement, which required minimum material, by determine the overall area, length and a suitable arrangement of Shell and Tube passes. 2. Short Report (Problem Statement, Formulation, Results and Conclusion) 3. Submission of softcopy of the report (in pdf) via LMS 4. Presentation

Problem Statement:
Design a tubular feed-water heater which need to heat the 1.5 kg/s of water from
20°C to 60°C.
Constraints:
a) Heating of water need to be done by saturated steam which is condensing at
1 MPa & heat transfer coefficients (on steam side) is 6500 W/m2K
b) Max. Velocity of water 1.0 m/s
c) Three different copper tube inner diameters 2.0 cm, 2.5 cm and 3.0 cm.
d) Thickness of copper tubes 10% of the inner diameter
Deliverables:
1. You need to provide the solution for the given problem statement, which
required minimum material, by determine the overall area, length and a
suitable arrangement of Shell and Tube passes.
2. Short Report (Problem Statement, Formulation, Results and Conclusion)

Answer 1

Firstly, the desired length of the tube needs to be calculated for the given conditions. The stream temperature will correspond to the saturation temperature of the steam at 1 MPa. The inlet and outlet temperature of water is known. The mass flow rate, convective heat transfer coefficient and the specific heat of water is also known. On Substitution into the formula, the required area of the tube can be calculated. Once the required area is obtained, the required length for different diameter can be obtained. From the obtained combination of diameter and length, the optimum is selected and some length for one pass is assumed and the number of passes required to meet the criteria for the length is calculated. The outer diameter of the tube is also calculated thereafter. The velocity criteria of maximum 1 m/s can't be achieved with the given diameter of the tubes. In order to limit the velocity to 1 m/s, the inner diameter of tube needs to be increased beyond 3 cm.

calculated Dexined length of tube needs to be Too T=179.88€ (Saturation Temp. of Steam at IMPa) Twi 20°c = 60°c wo L. m = 1.5 kg/h h = 6500 W/m²K (To - Two) To-To) Cep/hA MG = 4.18 IG/Kg.K 6500X A 679.08 - ) = capt 1179.88 - 60 179.98 - 20 1.5x4180 A = 0.28 m² = 1 ² 2 4 Requined tength 2 3 an, would be 565.om. For dia of an will be 884 m For dia of 2.5cm, Required length will be 565.068m For dia 392-96 m Required tength will be If we select diameter of tube to be 2.5cm, requined legtte Akturning length in one pass to be tom, the requuhed number of pacaeh cuould be 56.58257 20c = Twi -> - Length of Dach Taas = com Total Number 9 Potrer =57. → Tu = 60°c Saturated Steam at to = 179.88 °C x2.5x2 - 3 cm Outer diameter s tube d = 2.5+ ( +10)