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Heat ExchangersA heat exchanger, shown in Fig. P4.95, is
Chapter 4, Problem 95HP(choose chapter or problem)
Problem 95HP
Heat Exchangers
A heat exchanger, shown in Fig. P4.95, is used to cool an air flow from 800 to 360 K, with both states at 1 MPa. The coolant is a water flow at 15°C, 0.1 MPa. If the water leaves as saturated vapor, find the ratio of the flow rates ṁ water/ṁ air.
FIGURE P4.95
Questions & Answers
QUESTION:
Problem 95HP
Heat Exchangers
A heat exchanger, shown in Fig. P4.95, is used to cool an air flow from 800 to 360 K, with both states at 1 MPa. The coolant is a water flow at 15°C, 0.1 MPa. If the water leaves as saturated vapor, find the ratio of the flow rates ṁ water/ṁ air.
FIGURE P4.95
ANSWER:
Solution 95HP
Step 1 of 3:
A heat exchanger cools down the air with the help of a coolant (water). We are going to find the ratio of the mass flow rates.
The initial temperature of air T1 = 800 K
The final temperature of air T2 = 360 K
The pressure of airflow Pa = 1 MPa = 1000 kPa (constant)
The temperature of water T3 = 15°C
The pressure of water Pw = 0.1 MPa = 100 kPa