NONCONVENTIONAL PRINCIPLE OF CONVERSION OF HEAT INTO COLD IN AN INTERNAL COMBUSTION ENGINE NONCONVENTIONAL PRINCIPLE OF CONVERSION OF HEAT INTO COLD IN AN INTERNAL COMBUSTION ENGINE

The paper presents results achieved by a team of 12 researchers from the Faculty of Mechanical Engineering of the University of Žilina who participated in the solution of the project of the above-mentioned title within the period of the years 2002 – 2005. The basic research project focuses on the cooling internal combustion engine as an element of qualitatively new equipment designed for more effective utilization of fuel energy by a nonconventional progressive principle of heat conversion cooled by thermocompression. The issue of permanently sustainable life is approached from three hierarchical levels: a first level is a cooling internal combustion engine; a second level is a combined cogeneration complex power source; and a third level is a permanently sustainable power system. The cooling internal combustion engine is actually the basic element of the subsystem in the three-level complex of permanently sustainable life. It is still necessary to verify expected advantages of this unconventional combustion engine, potential savings of primary energy and foresee possible problems arisen during the simulation of the engine.


The project objective
The project objective is to carry out basic research into the fundamentals of a cooling combustion engine designed for more effective utilization of fuel primary energy by means of a nonconventional progressive principle of conversion of heat into cold through thermocompression. The subject of basic research is a nonconventional cooling combustion engine reciprocal movement of the piston and discontinuous combustion examined from the point of view of: a) theoretical analysis, b) consecutive mathematical modelling of thermodynamic and energetic states of the cooling combustion engine (taking into consideration the fact that it is the "cooling" engine), c) selection of components and media focusing on the increase of cooling output generated by the cooling combustion engine and on decrease of thermal losses.
All the above mentioned activities require a flow simulation of the coolant in the engine cooling system as a component of the absorptive cooling circuit with its analysis and consequent synthesis with the objective of designing a suitable configuration of the absorptive cooling circuit and suitable choice of coolant. To determine the data necessary for a mathematical modelling and subsequent verification of calculations and selection of components and coolants it is required: a) to design a testing model of the cooling combustion engine and for this purpose to accommodate the existing testing stand of the combustion engine, b) to carry out some experiments.
Expected social benefits are as follows: • extension of existing knowledge, dissemination of new knowledge -internationally oriented, • application of new knowledge into teaching materials of institutions of higher learning -professionally oriented, • transfer of knowledge into solutions of other applied reasearch tasks -specifically oriented, • enrichment of scientific and technical know how -specifically oriented aspect of solution.

Results of solution
The assessment is carried out chronologically in relation to the given objectives.

The year 2002
The following activities were carried out: 1. theoretical analysis and mathematical modelling 2. testing stand -reconstruction.
To determine thermal flows from the individual chambers of inserted cylinders it is necessary to know mass flows around the cylinders and temperatures in the corresponding places. This can be solved by a method of composition of the cooling system hydrodynamic elements characteristics. The dependence of specific energy on the mass flow in the cooling circuit can be described by the following set of equations: The resultant characteristic of the systems is given by the composition of individual characteristics of elements from Fig. 1, where the series connected elements are summed at a constant mass flow, the parallel connected elements are summed at a constant specific energy, Fig. 2.
Thermal flows from the individual chambers of inserted cylinders can be defined by means of the following equations: The year 2003 The following activities were carried out: 1. theoretical analysis and mathematical modelling: 3. experiments • Measurement of the engine surface temperatures -evaluation.
• Tests of the original engine -measurements of coolant flows.
• Mapping of the engine: characteristics, surface temperatures for two coolants (water, LiBr), assessment.
There was no agressive harm or damage of sample material, i.e. neither etching nor dissolving observed.
The following activities were carried out: • Modelling and computation of the inserted cylinder deformation.
• Geometry of the combustion engine cylinder generated in the ANSYS software.
• Thermal analysis of the cylinder.
• The final elements network. From the results of the computation it was found out the the liner was loaded mainly in the upper part some 22 mm from the head by a relatively high stress of 445 MPa. The displacements can be considered insignificant mainly due to their position (in the y-axis direction in the liner top and in the x-axis direction in the upper quarter of the liner.
Modelling and simulation of coolant flow and energetic flows.

A mathematical model for flow analysis
The analysis is based on a mathematical model for turbulent flow of "renormalized groups type -RNG k Ϫ ε -turbulent model". A renormalized procedure applied in turbulence lies in a gradual elimination of small turbulences. Simultaneously, equations of motion (Navier -Stokes equations) are transformed in such a way that turbulent viscosity, forces and nonlinear members are modified. Supposing that the turbulences are related to dissipation ε, then, ( 1 0 ) The averaged RNG model derived by a statistical method has formally the same shape as the classical k Ϫ ε model. The equation for transfer of momentum has the form: and, consequently, transport equations are used: For more details see [4].
Computed and measured data Tab. 2 Thermal flow from inserted cylinder. Tab. 3 Specification of places for measurement. Design of measure chain -sensors, transmitters.
The quality of the actual evaporation process is influenced by a constructional arrangement of the non-conventional cooling circuit of the combustion engine, pressure and temperature conditions under which the evaporation is assessed and concentration of alternative coolant. The cooling potential of atmospheric circuit is examined. Temperature conditions are defined by the boiling point of non-conventional coolant.
When compared with the former cooling system designed for tractor or automobile engines, for the non-conventional cooling system the following items can be defined: Mass equation of the non-conventional system: Total thermal flow Evaporation efficiency: Within further reconstruction (reconstruction -adjustment of temperature sensors, insulation of the evaporation container) the Q och Ͻ Q ch states are modelled at the atmospheric pressure. When defining this state it is necessary to follow trends of chosen parameters (oil temperature, exhaust gases temperature, flow through the block, temperature of the liquid at entering or leaving the engine, temperatures in the evaporation container, torque, consumption), which might clarify the transport of heat from the combustion space to the surface in the evaporation container.
Consequently, it is possible to define the value of a reduced output number as: If we are able -when realizing the complex cooling system in the required conditions -to define the state ⌬T ch ϭ 0 under suitable temperature and heat conditions on the combustion engine, then U tk ϭ 1. Then, it follows that we are able to maximally utilize after-expansion exergy in the cooling system and that we are also able to transform it into evaporation heat required for defining the cooling output of the absorptive unit.
Points for temperature measurement.

The year 2004
The following activities were carried out: 1. theoretical analysis and mathematical modelling • Drawing documentation for forced adjustments of the engine and test stand. • Checking and connecting the sensors for new tests, i.e. observation of the evaporation process, temperature states at intensification of evaporation under atmospheric pressure and consequently at underpressure. • Detailed topography of cavities of the engine cooling jacket, designed simplified virtual model of the engine cooling jacket, realistic meshing. • Modelling -meshing of the cavities of the engine cooling jacket -for calculation. • Solution of boundary tasks and conditions for the modelling of heat flows in the block. • Checking calculations and simulation of influence of changes in the boundary conditions. • Preliminary calculation (thermal balance) of quantities characterizing the state of coolant in particular places of the energetic circuit with the cooling combustion engine. • Tests of the engine with an adjusted cooling system with the evaporator to define the output reduced number. • The arrangement of the test stand and its control with the focus on automation of tests of the engine with a modified cooling circuit with an external pump in order to verify the results from the virtual modelling. All the investigated parameters were recorded and assessed with a computer programme.
Alternatives of the cooling system arrangement