--%>

Efficient use of waste heat and renewable heat sources

Efficient use of waste heat and renewable heat sources

1. Describe how you might recover heat from (a) a process exhaust gas stream (e.g. from an oven) and (b) a process warm water stream (e.g. from a commercial dishwasher). Discuss any aspects of the streams that may influence your choice of heat recovery system.

2. An industrial dryer operates for 60 hours/week, 50 weeks/year. It exhausts 200 kW/hr of heat and the value of the energy is 6p/kWh. A heat exchanger of 50% efficiency is put into the exhaust stream to recover a proportion of this heat. The installed cost of the heat exchanger is £22,500. The heat exchanger pressure drop needs a 2 kW fan to overcome it, and the cost of electricity is 10p/kWh

Calculate the simple payback period for the installation, taking into account the running costs, as well as the benefits.

3. A domestic air conditioning unit has a COPc of 2 Thinking of the refrigeration cycle and the inefficiencies in the various components, how could you attempt to increase the COP by modifying components?

4. The industrial dryer in Question 2 currently uses a heat exchanger for heat recovery. If the exhaust air is highly humid, as would be common on a dryer, there would be advantages in recovering latent heat as well as sensible heat. (Often you will find that the latent heat content is substantially greater than the sensible heat content).

Discuss how you might configure a heat pump which could recover the latent heat (and sensible heat) from the exhaust air then deliver it to the incoming fresh air. Is it possible now to recycle the exhaust air? If so, how would you reheat it?

5. Prime movers are being studied for powering combined heat & power (CHP) units in the home and in industry.

Sketch how the heat from these prime movers (e.g. a gas turbine, a small Diesel engine or another prime mover) can be recovered for (a) water heating, (b) providing chilled water (an outline of appropriate refrigerating equipment is required). 

   Related Questions in Mechanical Engineering

  • Q : Dynamic model for the paper machine

    Explain and derive the Dynamic model for the paper machine headbox?

  • Q : What is wrap-around Wrap-around : The

    Wrap-around: The main aim of a wrap-a-round is to make a straight line about a pipe to help in cutting the pipe to its appropriate length. It is employed mostly as a straight edge or a template.   

  • Q : Problem on Ideal gas process A) Air at

    A) Air at 4MPa and 3000C enters a will insulated turbine operating at steady state with negligible velocity. The air expands to an exit pressure of 100KPa. The exit velocity and temperature are 90 m/s and 1000C respectively. The diameter of the e

  • Q : Energy in the home-personal energy

    Energy in the home personal energy use and home energy efficiency. Estimate your personal Annual Energy Usage for the following - list all data in kWh (KiloWatt hours):

  • Q : Rated Speed and Economic Speed Explain

    Explain difference between the Rated Speed and Economic Speed?

  • Q : What is LILO What is meant by the term

    What is meant by the term LILO?

  • Q : Petroleum technology theories for the

    theories for the origin of petroleum, methods for detection of petroleum deposits, fractional distillation

  • Q : Calculating liquid composition There

    There is a 35% MeOH/water mix to feed to a flash at 100 Ib- mole /hr and 1 atm. We want a vapour composition of 60 % MeOH. What does the vapour flow rate need to be? What is the liquid composition? Give the equation of the operation line?

    Q : Advantages and disadvantages of using

    Explain advantages and disadvantages of using the LPG in Car?

  • Q : Problem on displacement response time

    (i) Formulate the equation of motion for the system shown in Figure below. List two assumptions made in this formulation. (ii) Find the response of this system at t = 3s. The system begins with the displacement of 5 cm and velocity