M.Sc Thesis

M.Sc StudentKootzenko Michael
SubjectProperties of H2O-N2-CO2 at High Pressures and Temperatures
for a Nitrogen-Based Alternative Fuel Power Cycle
DepartmentDepartment of Energy
Supervisors PROFESSOR EMERITUS Yeshayahou Levy
PROF. Gideon Grader
Full Thesis textFull thesis text - English Version


Extensive release of CO2 into the atmosphere believed to be the main cause in the process of Global warming and subsequently has an adverse effect on human health and welfare. Both are directly linked to future energy production. A Nitrogen based alternative fuel was previously suggested offering an energy storage scheme and carrier solution, ensuring a safe, affordable and convenient solution for reducing  CO2  levels by reaction R1 below: 3NH4NO3(l) N2H4CO(l) 5.56H2O(l) à 13.56H2O 4N2(g) CO2(g).

The fuel’s Reaction products are exhausted in the gaseous state with pressure conditions (constant pressure reaction) that can be set in the range of 50-250[bar], and temperature conditions ranging at 1100[˚C]. We propose to use the products of this reaction (R1) as the working fluid for a dedicated power cycle.

Power cycles such as the Rankine, Kalina, and the Binary cycle, all work on vapors such as water, refrigerates, ammonia etc. Other cycles such as the Otto, Diesel, Stirling, and Brayton cycles work mostly on gases such as air-mixtures, helium, and other basic ideal gases. A key factor in the design and analyses of such a power cycle are the properties of the working fluid.

Many models and correlations were developed over the years to investigate fluid mixtures. These models are often inaccurate at high pressures, and often do not correspond to actual data. Furthermore, no experimental data that deals with these (R1) working fluid’s properties was published.

In this thesis, we propose a feasible thermodynamic OCICE (Open Cycle Internal Combustion Engine) design, and specify the mathematical model that suites the proposed working fluid, by investigating its thermodynamic characteristics. The thermodynamic properties of interest are the compressibility factor “Z”, the saturation conditions Pv, Tv, and the specific isobaric heat capacity Cp of the working fluid. To provide such data an experimental facility was used in the form of a close constant volume vessel. Pre-defined nitrogen-carbon dioxide mixture reservoir at 4:1 N2 to CO2 ratio, and liquid water was used. The vessel was heated to 500[˚C] and then spontaneously cooled to room temperature. Pressures and temperatures of the working fluid were measured during the process.

The value of the Compressibility factor “Z” as calculated from the experimental results was compared to different analytical theoretical EOS equations, and it was found that the Twu et al - 1995 EOS coupled with a molar weighted additive critical pressure average is the most compatible model with under 2% deviation at temperature range of 600-750[K] and pressures up to 220[bar]. In addition, the saturation data, obtained from the measurements during condensation of the products (R1), were compared to that of pure H2O . It was found that the Dalton of additive pressures method is an appropriate method to predict the saturation conditions of the working fluid.

For last, a simple case of OCICE was examined for reaction conditions of 250[bar] and 1100[˚C]. The cycle was found to produce 2755[J/gram-AN] of work, at an efficiency of 49% in relation to the fuel’s HHV (High heating value).