# Section 1: Engineering and Chemical Engineering Q1. A hydroelectri...

## Transcribed Text

Section 1: Engineering and Chemical Engineering Q1. A hydroelectric power plant uses the reaction of cthylene (C2H4) with oxygen to generate vapour. The products of this reaction are carbon dioxide and water. a) How much ethylene is required by the power plant if 6500 kg of steam at 120 C is produced in an hour? (assume 100% yield) b) Recalculate your answer for a 75 % yield. Assumptions. The heat capacities of water are - = 1996 KI/Kg°C the heat of vaporization for water is AR, - 2256.9 x1/185 and the power plant takes water from a source at 15°C. Q2. Water is flowing in a fire hose with a velocity of 1.0 m/s and a pressure of 200kPa. At the nozzle exit, the pressure decreases to atmospheric pressure (101.3kPa), there is no change in height. What is the velocity of the water exiting the nozzle? Q3. Water flows from an elevated reservoir through a pipe to a turbine at a lower level and out of the turbine through a conduit of similar diameter. At a point 50 m above the turbine, the pressure is 307kPa, and at a point 10m below the turbine, the pressure is 110 kPa. What must the water flow rate be if the turbine output is 0.5 MW? Q4. Pasteurization is a common practice in the production of milk and juices. A company processes 5000 litres of milk per day. The milk is pasteurized in a heat exchanger by raising the temperature of the milk from 5 °C to 80 °C. This heating process is carried out on a heat exchanger which has an overall heat transfer coefficient (U) of 40 a) Calculate the amount of heat required per hour to pasteurize 5000 litres of milk per day. The heat capacity of milk is 3.77 k] lkgo the density (p) of milk is 1.038/cm2 b) Calculate the temperature of the water leaving the heat exchanger if the heat exchanger uses water at 100 °C to heat up the milk and the mass flow rate of water used is 400kg/h c) Use the design equation for heat exchangers to calculate the requires area for the heat exchanger.

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Q1. A hydroelectric power plant uses the reaction of ethylene (𝐶2𝐻4) with oxygen to generate vapour. The products of this reaction are carbon dioxide and water.
a) How much ethylene is required by the power plant if 6500 kg of steam at 120 ℃ is produced in an hour? (Assume 100% yield)
b) Recalculate your answer for a 75 % yield.

Assumptions.
The heat capacities of water are
C𝑝𝑙=4.19kJ/kg℃,
𝐶𝑝𝑣=1.996 𝐾𝐽/𝑘𝑔℃,
the heat of vaporization for water is Δℎ̂𝑣=2256.9 𝐾𝐽/𝑘𝑔,
and the power plant takes water from a source at 15 ℃

Solution
C2H4+1/2O2    =    C2H4O (Mediate reaction)

Reaction C2H4 + 3O2 = 2CO2+2H2O ( Main reaction)

Molecular weight C2H4=28, O2= 32, H2O=18

Sol: Basis: One hour of operation at 120 deg C

Steam production (water) =6500kg of steam/hour
Mole of steam (water) =6500/18= 361.11kmol
Since C2H4=2H2O

C2H4 reacted=1/2* H2O(Produced)
=0.5*361.11kMol
=180.555 kMol...

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