This assignment comprises of 2 different elements. In the first portion you need to choose or design a heat exchanger for a waste heat recovery system in cars. The second portion is a reflective journal regarding the unit, a bit similar to the SETU problemnaire however mandatory to capture the thoughts of all students.
The assignment requires to be submitted through CloudDeakin as a MS Word or pdf file.
Heat Exchanger selection/design:
Suppose you are part of a product development team which is developing a novel waste heat recovery system to make cars more efficient. One of the features of the system is to transfers wasted exhaust heat to the engine oil through a heat exchanger to decrease the friction of the oil, particularly during warm up, but as well during steady state operation at engine loads below wide open throttle. Your task is to either design or choose and source an existing heat exchanger which will be appropriate for this application. Even although most driving patterns in a car are highly dynamic you are given most operating conditions as average over the legal fuel consumption drive cycle. In the assignment you require to justify the decisions based on you engineering judgment and by applying the concepts you learned in the heat transfer unit.
The priorities for the latest product are as shown below:
1) Safe operation beneath all possible operating conditions at ambient temperatures between -30 °C and +50 °C
2) Maximum efficiency of the heat exchanger to be capable to realize the highest possible fuel economy improvement
3) The durability of 150,000km (legal necessity for emission relevant components).
4) Low weight to minimize the negative impact of additional weight towards fuel economy.
5) Small external volume to make it simple to package it in the packed and tight engine compartment.
6) Low cost.
7) Low external temperatures to avoid deterioration, aging or long term damage of close by plastic components.
8) Long term resistance against the fouling.
Operating conditions:
The given operating conditions must be considered in your selection or design procedure:
a) The test condition is the New European Drive Cycle (NEDC), the duration is 1180 sec.
b) The exhaust gas comprises of corrosive combustion products. The average water content is around 10%
c) The average exhaust temperature to the heat exchanger is 434 °C throughout the NEDC.
d) The maximum exhaust gas temperature is 625 °C throughout the NEDC.
e) The ambient air temperature is 24 °C throughout the NEDC; this doesn’t change over the test cycle.
f) The start temperature of all the engine components inclusive exhaust gas heat exchanger and the engine oil is as well 24 °C
g) The average flow rate of exhaust gas is 6.9 g/s.
h) The average oil flow rate is 10 l/min.
i) The average oil temperature is around 60 °C.
j) The average vehicle speed is 35km/h, the wind speed is simulated proportionally to the vehicle speed through a vehicle cooling fan.
k) The average exhaust heat flow throughout the NEDC is 4kW.
l) The target exhaust gas temperature subsequent to the heat exchanger is to be beneath 90 °C throughout most parts of the NEDC to be able to utilize the condensation enthalpy of the water as much as possible.