Reference no: EM13863069

Heat Transfer Assignment

This assignment consists of 2 different elements. In the first part you need to select or design a heat exchanger for a waste heat recovery system in cars. The second part is a reflective journal about the unit, a bit similar to the SETU questionnaire but mandatory to capture the thoughts of all students.

The assignment needs to be submitted through CloudDeakin as a MS Word or pdf file.

Part 1 - Heat Exchanger selection/design

Imagine you are part of a product development team that is developing a novel waste heat recovery system to make cars more efficient. One feature of the system is to transfers wasted exhaust heat to the engine oil via a heat exchanger to reduce the friction of the oil, particularly during warm up, but also during steady state operation at engine loads below wide open throttle. Your task is to either design or select and source an existing heat exchanger that will be suitable for this application. Even though 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 need to justify the decisions based on you engineering judgement and by applying the concepts you learned in the heat transfer unit.

The priorities for the new product are as follows:

1. Safe operation under all possible operating conditions at ambient temperatures between -30 °C and +50 °C
2. Maximum efficiency of the heat exchanger to be able to realise the highest possible fuel economy improvement
3. Durability of 150,000km (legal requirement for emission relevant components)
4. Low weight to minimise the negative impact of additional weight towards fuel economy
5. Small external volume to make it easy 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 nearby plastic components
8. Long term resistance against fouling

Operating conditions

The following operating conditions should be considered in your selection or design process:

The test condition is the New European Drive Cycle (NEDC), the duration is 1180 sec

The exhaust gas consists of corrosive combustion products. The average water content is about 10%

The average exhaust temperature into the heat exchanger is 434 °C during the NEDC

The maximum exhaust gas temperature is 625 °C during the NEDC

The ambient air temperature is 24 °C during the NEDC, this doesn't change over the test cycle

The start temperature of all engine components inclusive the exhaust gas heat exchanger and the engine oil is also 24 °C

The average flow rate of the exhaust gas is 6.9 g/s

The average oil flow rate is 10 l/min

The average oil temperature is 60 °C

The average vehicle speed is 35km/h, the wind speed is simulated proportionally to the vehicle speed by a vehicle cooling fan

The average exhaust heat flow during the NEDC is 4kW

The target exhaust gas temperature after the heat exchanger is to be below 90 °C during most parts of the NEDC to be able to utilise the condensation enthalpy of the water as much as possible