Fundamental Principles of Thermodynamics and their Application in Engines

You have recently gained employment at an engineering test facility, which is renowned locally for its industrial excellence. Your line manager is undecided where to place you within the organisation, so she has asked you to complete the following tasks to demonstrate where your skills can be best utilised.Using the candidate number allocated, present your response in a manner which would be deemed fit to present to your employer.

Produce a booklet for use by the training department that describes the fundamental thermodynamic operating principles listed below. To ensure the employees understand the concept give a practical examples of these principles using the internal combustion engine and a gas turbine as the basis for examples, give typical properties and operating parameters you would expect.

1. The Zeroth law and its importance.

2. Heat

3. Internal energy

4. Enthalpy

5. The control volume

6. System boundary

7. Working fluid

1. The first law of thermodynamics forms a one of the key foundations for understanding the operation of the engines in both parts of the business. Explain the application of the law and use either the example of an internal combustion engine or a gas turbine to illustrate its application, reference to heat and work must be included.

2. A group of the employees from the gas turbine company have found it difficult to understand the concept of ’boundary work’ using a suitable diagram of engine cylinder describe the concept.

3.Using the same diagram show the sign convention for defining heat transfer between a system and its surroundings.

The question below is typical of the applications you may find in both businesses with a three stage process, use this example to give a typical calculation for final pressure.

A gas container with a volume of 0.4m³ and pressure of 124kN/m² is compressed to 90% of its original volume with a 14% increase in temperature from its original temperature of 70°C.

After compression 10% of the gas by mass is removed with no change in temperature.  

Calculate the final pressure.

The molecular weight of the gas is 28.

To assist understanding plot the above process on a Pressure-volume graph (PV) and explain the relationships between the constants.

A steam plant originally installed by the turbine company is located very close to the parent company and the maintenance engineers from the parent company have been asked to familiarise themselves with the system. To help them you have been asked to consider the process below, firstly:

Task 2

Draw a schematic of the system, clearly identify the flow and define its boundary and working fluid.

Then working from first principles develop an energy equation for the heat and work input/output from the system. From your equations calculate the amount of steam flowing round the system described in c. Your answer must be in Kg/s.

A gas boiler supplies steam to a turbine, which is then recycled through a condenser, which dumps the thermal energy to a water system, it is then pumped back into the boiler by a feed pump.

The plant develops 2300kW the heat supplied to the boiler is 3000kj/kg the heat rejected by the system in the cooling water and condenser is 2300kj/kg. The feed pump requires required to pump the condensate back into the boiler is 9.5kW.

The new company has a test facility with some unused gas test equipment an apprentice has supplied you with the following information about the equipment.

 A piston-cylinder device is activated by a 2,500kg mass that falls under gravity two metres to compresses 0.8 kg of nitrogen.

The nitrogen is initially at atmospheric pressure, 100 kPa and 27°C. The nitrogen is now compressed slowly as the mass falls until it is half its initial volume and the temperature has risen to 94°C. The process is considered to be polytropic during which   PVn= Constant. All work done on the gas comes from the falling mass, however, 5kJ of energy are lost from the cylinder.

Find the value of n the index of compression.

A compressed air cannon is used to deploy a life boat over the side of a boat, the life boat inflates when it makes contact with the water.

The system has been modified to increase the energy release and the distance it is thrown over the side, by heating the compressed air prior to deployment. You have been asked to check the system out puts as described below and write a short brief describing the systems operation for your manager. Reference to the non-flow equation is required in this brief.

Compressed air in a cylinder has an internal energy of 420 kJ/kg at the beginning of an expansion process, and an internal energy of 200 kJ/kg after expansion. Calculate the heat flow to or from the cylinder when the work done by the air during expansion is 100 kJ/kg.

A steam plant originally installed by the turbine company is located very close to the parent company and the maintenance engineers from the parent company have been asked to familiarise themselves with the system. To help them you have been asked to consider the process below, firstly:

Draw a schematic of the system, clearly identify the flow and define its boundary and working fluid.

Then working from first principles develop an energy equation for the heat and work input/output from the system. From your equations calculate the amount of steam flowing round the system described in c. Your answer must be in Kg/s.

A gas boiler supplies steam to a turbine, which is then recycled through a condenser, which dumps the thermal energy to a water system, it is then pumped back into the boiler by a feed pump.

The plant develops 2300kW the heat supplied to the boiler is 3000kj/kg the heat rejected by the system in the cooling water and condenser is 2300kj/kg. The feed pump requires required to pump the condensate back into the boiler is 9.5kW.

The company has two diesel-powered standby generators, both of which are capable of supplying sufficient electrical power in the event of a failure. Both diesel engines have the same details on their name plates (given below), but one operates on the four-stroke cycle, whilst the other operates on a two-stroke cycle. As all the other information has been lost, you have been asked to determine the indicated power, the brake power and thus confirm the mechanical efficiency of each engine.