Answer—

1) Advantages an Disavantages of waste heat recovery :

Basically, Heat recovery refers to the process of reclaiming a portion of the energy which is wasted by the use of Heating Venting and Air Conditioning (HVAC) systems.

Advantages _

> Reducing energy costs-

Each unit of recovered waste heat directly replaces each unit of purchased energy, that means is reduces energy costs.

> Reducing the cost of capital equipment-

Reuse of waste heat results in the use of smaller energy conversion equipment, which reduces capital outlays and offsets the cost of heat recovery systems. The reduction in fuel consumption reduces flue gas generation and fosters a reduction in the size of equipment required to handle flue gases, such as fans, stacks, ducts, burners, etc.

> Lowering operating cost-

Waste heat recovery reduces energy cost and also total operating costs.

> Reducing environmental impact-

By this reduces carbon emissions so by this environmental impact on the air and water aslo reduces.

Disadvantages_

Some waste recovery equipment installations may not match the full recovery potential due to the material limits of the heat exchanger or the expense of extending recovery techniques to lower-temperature and higher-temperature systems.

Most unrecovered waste heat comes from low-temperature systems ( below 232°C ), which has low thermal and economic value. Nonetheless, the magnitude of low-temperature waste heat is hard to ignore, and it offers tremendous opportunities for waste heat recovery.

Also in some industries, waste heat may be prohibited because of the source of chemical composition or because the recovery effort may not meet the required volume to be cost-effective.

2)

Common point between Atkinson and Miller cycle :

> Both are delayed valve-closing method.

> Both Atkinson cycle engine and Miller cycle engine are type of over-expansion cycle engine.

> Also many modern engines now use unconventional valve timing to produce the effect of a shorter compression stroke/longer power stroke. Miller applied this technique to the four-stroke engine, so it is sometimes referred as the Atkinson/Miller cycle engine.

A miller cycle engine is very similar to a modern Atkinson cycle engine. However, there are some differences;

> A miller cycle engine depends on a turbocharger or supercharger but Atkinson not depend.

> A miller cycle engine has either an early or late intake valve closing during the compression stroke. When the intake valve closes late, the piston travels 20 to 30% of the way back up to the top of the cylinder before the intake valve finally closes, so that the engine compression starts at the pressure of the turbocharger or supercharger.

But the Atkinson cycle delays the intake valve's closing until the piston has completed 20 to 30 percent of its upward travel on the compression stroke.

> Miller-cycle engine uses some device to push air into the system, a supercharger or turbocharger. While the Atkinson-cycle engine is naturally aspirated.

Comparing with Otto cycle engine to Miller cycle engine :

In the Miller cycle, the intake valve is left open longer than it would be in an Otto-cycle engine.

The Miller cycle engine is compared to a standard Otto cycle engine using cycle analyses and multidimensional simulation, and basic engine design implications are discussed. It is found that the Miller cycle engine has a potential for improved fuel efficiency, but at the cost of a reduced power to weight ratio. A fuel efficiency advantage of 5 to 10% compared to a standard Otto cycle engine.

Comparing with Otto cycle engine to Atkinson cycle engine :

An Atkinson cycle has a greater work output and a higher thermal efficiency than the Otto cycle at the same operating condition.

The compression ratios that maximize the work of the Otto cycle are always found to be higher than those for the Atkinson cycle at the same operating conditions.

Design philosophy of miller cycle :

The Miller cycle is a thermodynamic cycle used in a type of internal combustion engine.

The engine may be two-syroke or four-stroke and may be run on diesel fuel, gases, or dual fuel.

Design philosophy of Atkinson cycle :

The Atkinson-cycle engine is a type of internal combustion engine.

The Atkinson cycle is designed to provide efficiency at the expense of power density.

Atkinson produced three different designs that had a short compression stroke and a longer expansion stroke.

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