събота, 17 октомври 2015 г.

thermodynamic - mechanical puzzles

Some thermodynamic - mechanical puzzles
1. drawing


2.drawing




drawing 3


drawing 4




What power we will need to rotate the crank?
It will change the temperature of the working substance?

drawing 5




Win/Wout = ?

drawing 6



Wout > Win ?

drawing 7

Wout > Win ?

drawing 8



Wout / Win = ?

drawing 9



Wout / Win = ?

drawing 10



Wout / W in = ?

понеделник, 5 октомври 2015 г.

Points of view

To be more clearly what happens with heat, what about the cold, whether we lose (to be warm up ) the cold part will present two perspectives that I hope to be useful to readers:

1. Will present the method from the following perspective - look at turbine as cooler.
 Turbines and cooler removes heat from a given substance, as the turbine makes transforming the heat of the substance into mechanical energy, and cooler removes heat from the substance as gives this heat to the other body by heat exchange. So thus each turbine is a cooler for the previous turbine - transforming waste heat into mechanical force in a closed cycle of its working substance. So for aggregate with n of number of turbines will have to "pay" for cooling only the last, and n-1 of number turbines will have a "free" cooling. After each cycle of working substance the amount of waste heat progressively reduces, as to cooler of last turbine remains small amount of kilowatts of heat, because turbines are turned into mechanical energy initial amount of heat.
To be equal power between the turbine and the cooler (useful to opposite) there must be equality:
- Temperature difference that will have substance before and after the turbine has performed work, and the temperature difference to which the cooler will cool the substance and the temperature on the body which receive this heat

- Kilowatts of heat which turbine converts into mechanical force to be equal on kilowatts of heat that the cooler will take from the substance and will transmitted to another body

But comparing:
-Kilowatts of heat which the turbines are turned into mechanical power and kilowatts of heat that the cooler has to take from the substance and to transmitted it to another body
-The temperature difference between the hot and cold part of the unit, and the temperature difference between the hot and cold part of the cooler:
 Useful forces exceed the force that we will need to apply on compressor of cooler to perform its task - to provide a precondition of the last turbine to work, and hence the entire unit to work.


2. Another point of view: The turbine and compressor are not on the same axis (drive shaft),and supply compressors and pumps with external force. For example - supply compressor and pumps from an electric grid, and turbines operate independently produceing energy to be transmitted to the grid.

Let in a thermodynamic system designed by the "external combustion - internal cooling" method  a compressor of cooler powered by external force creates prerequisite of a last turbine to operate. By doing this work turbine creates a prerequisite of another turbine to work, and for 3 turbines unit - the work of the second turbine creates the premise of the first turbine to work.
For example - Compressor on cooler with a capacity of 100 kW .
These 100kW power of the cooler can "take" 100 kW heat of a substance and it to him back*. Assuming that the turbines convert 50% of the amount of heat into mechanical energy , from 200 kW waste heat from the previous cycle, the turbine converts into  mechanical energy 100kW, and 100 kW remain  a waste heat which the cooler should "deal".
200kW of waste heat for the second cycle -  so it goes:
200kW of mechanical force + 200kW of waste heat = 400kW
For the first cycle:
400kW mechanical work + 400kW waste  heat = 800kW
 (Here may momentarily confusion in the reader, because the last cycle differs from the previous in that the waste heat is returned to the cycle, but it will only mean a large amount of the circulating working substance in it.)
 Thus, for a unit with three working substances and three turbines account is as follows:
- From a grid will draw 100kW for compressor on cooler
+ The turbines will return to the grid 400 + 200 + 100 = 700 kW power
To this we must add the energy that will take from electricall grid to drive the pumps.


*I accept that if:
- As a result of work done from a turbine by turning some amount of heat into mechanical energy of a given working substance, a working substance cools with  N°  degrees
  - Cooler to take the same amount of heat from the same substance and transmit it to another body in which overcomes the same temperature difference as it is created the turbine (N °)
  The mechanical force which produces turbine and the force which need to apply the compressor on cooler over working substance are the same.