Perishables requested by consumers all over the world are transported intensively and request no interruption of the cold chain. In this context, cold chain logistics, quality and safety of the products together with convenient comprehensive cost of cold chain transportation are under the attention of all actors involved in the process. Refrigeration is the technology with a key role in this activity. It is a technology with high energy consumption and rises environmental problems. In this paper cold chain transportation is approached multidisciplinary, so that this manuscript can be used as a guidance for different specialists. Are provided fundamentals of vapour compression refrigeration systems and formulae for costs affecting the total cost of this activity. It is taken into discussion multimodal transport, being considered costs reflecting on shore and on board transport of perishables.

In order to increase the knowledge of future marine engineers it is needed to bring closer the practical skills with theoretical gains. In Constanta Maritime University, Marine Refrigerating Plants is a discipline included in the curricula of future marine engineers. Practical learning can be also developed on low cost and effective means – as it will be proven in the paper. By using Coolselector 2, future marine engineers are trained to apply theoretical knowledge such as thermodynamics principles and to better understand the vapour compression cycle analysis, thermodynamic properties of refrigerants or the importance of the main components of a basic vapour compression refrigeration cycle. At the end of the practical session, students will gain important skills specific to theoretical aspects of refrigeration and thermodynamic processes and real situations.

Internalization is a process affecting almost all the aspects of our modern life, including higher education. Integration of international students is quite challenging for host universities and it requires institutional strategies enabling academic well-being and progress on campus. Maritime transport affects in a major way the global economy because it is related with different industries. Its fast development implies highly skilled seafarers, with technical and inter-cultural communication skills, since ships are operated by multicultural crews. For the maritime sector, multiculturalism is a situation firstly met in higher education institutions, and then on-board the ships. The goal of this article is to explore how an inexperienced welcoming activity can contribute to the integration of international students in Constanta Maritime University. The activity was conducted as a debate on shipping- climate change- religious beliefs linkage and has gone at the beginning of the current academic year. Participants were recruited from junior international students and senior Romanian students. A total of 42 students agreed to take part in the debate and to form three groups: pro team (Christians and Muslims), con team (seculars) and audience (Christians, Muslims, Hindu and seculars). Both teams showed strong pro-environmental values, expressed by different approaches: believers focused on stewardship, while seculars on empirical evidence. The conclusion of the debate, stating that bridging shipping, climate change and faith is appropriate and fruitful and that this theme improved communication between students with different values, was approved by 93% of participants.

Seafarers' cultural background is an important factor when talking about appropriate working conditions and daily life activities on board the ships. Nowadays, merchant ship crews are multinational. This is why nautical students should be prepared to face with intercultural differences during their training education. It is time to admit that, in this particular situation, standardised teaching methods might be insufficient. In this respect, we tried to integrate students' faith to our teaching, in order to facilitate learning and integration of international students. The present case of study deals with international students enrolled in the study program called 'Navigation and Maritime' and 'River Transport', second and third year of study. It is about 83 international students and two lecturers teaching 'Heat transfer and Thermodynamics' and 'Meteorology and Marine Hydrology'. The findings of this descriptive qualitative research indicate that implementing faith knowledge of students in the teaching process allows a better understanding of theoretical knowledge and a smoother integration in the focused multicultural groups, as seen at the end of the semester.

Heat exchangers are thermal devices used in several industrial applications. Parallel flow arrangement means that both fluids flow stream is in the same direction. Low thermal conductivity of traditional fluids affects in a negative manner the efficiency of heat exchangers. In order to overcome this drawback, literature recommends the use of nanofluids. This paper deals with a theoretical study of performance enhancement of a double pipe heat exchange with parallel flow arrangement. The analysis consists in a comparison between the situations in which the water and the water base nanofluid (Al2O3-water) are the cooling fluids. The cold fluid is a nanofluid (NF)- represented by Al2O3 nanoparticles added to water. The diameter of nanoparticles is 25 nm and the considered volume concentration is of 0.25%. The hot fluid is water. The nanofluid flows in the outer pipe, while the water flows in the inner pipe; fluids flow with constant inlet temperature: 32°C – for the nanofluid and 58°C – for the water. The volumetric flow rate varies in the range: 0.5÷1.9 L/min. The obtained results show that the average values of the following: heat transfer rate, effectiveness, inner and outer heat transfer coefficients, all for the nanofluid, are about 16%, 10%, 16% and respectively 17% higher in comparison to the base fluid. The analysis will reveal the fact that a better performance of the heat exchanger it is achieved when using Al2O3-water nanofluid as a cooling medium than when using the base fluid (water), due to the higher thermal conductivity of the nanofluid.

Part- time education is very attractive for students and universities, due to its obvious benefits related with economic, mobility and friendly education environment aspects. In Constanta Maritime University, part- time education is available for marine engineering, electrical engineering and navigation and waterborne transport programs. According to the Romanian legislation, the evaluation of part- time students consists in two types of assessment: formative evaluation and final evaluation. The formative evaluation is carried on by the use of the university’ E- Platform, while the final evaluation is face to face type- exactly like the one of full- time students. In the case of study, it is described the formative evaluation of part- time students enrolled in Marine Engineering program, second year of study, in the case of students’ performance assessment in Thermodynamics 1 Course. There are enrolled 52 students, but only 25 attended the formative evaluation, despite of the fact that this evaluation has a percentage in the final grade. This paper describes the manner in which this evaluation took place. Also, where analysed the reasons for not attendance and mistakes in test solving. Where identified the ways in which students performance might be improved, for a better understanding of the curricula.

Marine refrigeration has to comply with environmental constraints and with efficiency improvement as well. R22 was a refrigerant governing marine refrigeration systems. After 2020, it is legally in use in old systems, relying on recycled supplies, because of its poor environmental properties. In this paper, it is developed a theoretical analysis of a single stage vapour compression system working with R22, on basis of energy and exergy analysis. The thermodynamic analysis consists in the assessment of the influence of evaporator temperature on the performance of the system- by the use of the laws of thermodynamics. The evaporation temperature varies in the range (6.5-9.5) oC, when the ambient temperature is 28oC.The obtained results will show that the Coefficient of Performance will increase together with the evaporator temperature increase, while the specific work consumption and specific total exergy destruction will decrease. For the maximum considered value of the evaporator temperature, COP value increases with 14% in comparison with the value obtained for the minimum evaporator temperature. In addition, the specific work consumed by the compressor will decrease with 5.81%, while for the specific total exergy destruction the decrement is of 2.4%. Seen that for the highest evaporator temperature it is reached the performance improvement, for 9.5oC are also determined the exergy destructions in the main components of the system. It is found that in the compressor, in the evaporator, in the condenser and in the throttling valve, exergy losses are 5%, 36%, 56% and 3%. Exergy analysis reveals that the most inefficient components of the system are the two heat exchangers of the system.

"Adding of nanoparticles in a base working agent leads to Nano fluids representing of a new type of working fluid. Due to an increase surface area, there is a gain in the surface area needed for heat transfer between nanoparticles and base fluid. Sein the poor heat transfer properties of water, water base Nano fluids present improved heat transfer performance and require smaller heat exchangers. This paper deals with the estimation of specific heat transfer capacity of water-Al2O3 Nano fluid. The decrease of volume concentration, from 13% to 3%, will reveal a gain in SHC of 27% - for nanoparticles diameter of 60 nm and a gain of 40% - for 30 nm diameter. At high temperature, SHC shows better values, also when the volume concentration is lower."

Vapour compression refrigeration systems (VCRS) are present in various applications of refrigeration; they work with high power consumption and rise environmental concerns. Important features of VCRS working with R134a are reflected in significant energy consumption and environmental issues. This is why the analysis of performances terms, such as power consumption and Coefficient of Performance (COP), is mandatory. The adoption of nanorefrigerants is a promising step towards new working fluids to be used in refrigeration systems. The environmental issue specific to the traditional R134a can be diminished by replacing it with nanorefrigerants- resulted by adding of nanoparticles to the pure refrigerant (R134a). Traditionally used R134a contributes to the global warming. This problem is associated with the need to improve the efficiency of the plant. The solution is the adoption of a new refrigerant: the nanorefrigerant. This paper focuses on the performance improvement of VCRS working with R134a and R134a/Al2O3. The theoretical comparison is developed considering the evaporator temperature of –10° C and a condensing temperature in the range (30÷50)° C. The performance of the system is analysed in terms of work consumption and COP. Since the adoption of R134a/Al2O3 will reveal a gain in the energy efficiency (13%) when rising the condensing temperature, the analysis will continue with the performance assessment when the concentration of nanoparticles will vary in the range (0.05÷0.50)%. Results indicate that a 10 times increase in Al2O3 concentration will lead to about 77% decrease in work consumption.

R134a is a refrigerant met in several marine refrigeration applications, such as fishing vessels, passenger and cargo ships. In 2014, 26% of the international commercial fleet was using R134a. Although R134a shows a null Ozone Depletion Potential, it has a quite high Global Warming Potential (1300). R134a is a greenhouse gas and, even if it is present on newer ships, the future will be marked by its replacement with substitutes having low GWP. Still, because its GWP is less than 2500, R 134a will continue to be used. Due to the fact that vapour compression refrigeration systems are dominant on board the ships and knowing that these technologies are high energy consumers, analysing their performance in the contemporary energetic context, is imperious required. This paper presents a theoretical analysis of a single stage vapour compression cycle, working with R134a, based on the laws of thermodynamics. The analysis will reveal the influence of the evaporator temperature on the Coefficient of performance and on exergy efficiency, and also the influence of sub cooling on these two efficiency terms, on the refrigerant mass flow rate and compression rate. It was considered a variation of the evaporator temperature in the range (-40÷ -10)oC and of the sub cooling in the range (0÷10)oC. The increase of the evaporator temperature will contribute to a COP increment (50%) and an exergy efficiency decrease (34%). The sub cooling will lead to both COP and exergy efficiency increase (11%). Higher sub cooling degree will provide an increment in the refrigerant mass flow (18%) and a decrease of the compression rate (76%) meaning lower work consumption at the compressor.

As well known, the day of 11 March 2020 will remain in the history as the day in which The World Health Organization (WHO) has declared COVID-19 a pandemic. Under these circumstances, the international higher education was forced to remove the campus activities in online. Constanta Maritime University is one of the universities across the world which moved the educational process from face- to- face to online learning. This was a challenging task for the academic, managing and technical administration and for the students, as well. This paper focuses on the disciplined entitled Thermodynamics 1, encountered in the curricula of the Electromechanics Faculty, Constanta Maritime University. The paper describes the steps done during the online education along the semester, both by students and lecturers. At the end of the semester, students and lecturers had to face another challenge: the online examination. Since in the new conditions, the students had to gain the same knowledge as during the classic educational process, we are providing the results obtained by our students. Their exam was scheduled on June 26, 2020. The number of students attending the online examination was 108. The online report for the examination, available on the online platform of the university, indicates that online 17 students were not able to pass the examination (grade 5). The same chart data shows that 19 students have obtained grades in the range (8,00- 8,50), while 2 students obtained grades in the range (9, 50- 10,00). These results are considered to be encouraging for lecturers and students. This type of examination it is seen as a potential long term examination manner, given its benefits: online generation of the test, online verification and not last, transparency.

R22 is a refrigerant that has dominated marine refrigeration onboard fishing vessels till 1 January 2015. Because in its composition exist ozone-depleting chlorine atoms, this refrigerant needs acceptable substitution solutions, to achieve the ozone protection desiderate. For R22 was not found a unique replacement solution. This paper investigates the opportunity to substitute R22 with the refrigerant R 417A, due to its very close thermodynamic properties to R22 and, moreover to its friendly behavior to the ozone layer. Seafood consumption is permitted for Muslims, fishing activity being important for these communities. Fishing depends on vapor compression refrigeration technology, equipment known to be an important energy consumer. In this paper, it is shown that environmental preservation is important in the refrigeration industry and in Islam, as well. The theoretical analysis developed in this paper focuses on the seawater cooling system onboard fishing vessels while catching in tropical waters. The investigation has energetic, environmental, and Islamic components. The comparison between the plant working with R22 and with R417A reveals that the ecologic refrigerant represents a wise solution for retrofitting existing plants.

This paper investigates the comparison between single stage vapour compression refrigeration cycles working with R134a - a traditional refrigerant for marine applications, and R435A - a new refrigerant having Dimethyleter (DME) 80% and R152a 20%. Since R134a shows a high GWP (Global Warming Potential), in the next future this refrigerant will be a subject for replacement. The new refrigerant taken into discussion here, R435A, shows a much lower GWP (3 compared with 1300 of R134a). The study allows the investigation of the performance of the cycles working with these two refrigerants, within a thermodynamic analysis, based on both first and second laws of thermodynamics. This kind of research is a strong tool used in design, optimisation and performance assessment of refrigeration systems. In the present paper are analysed the influence of evaporation temperatures on first and second law efficiencies and on exergy losses in the system. The results are obtained when this temperature varies in the range (248÷278) K. These results reveal the fact that R435A is a viable solution for R134a replacement, since average COP for R435A is about 35% higher than for R134a, the average exergy loss is around 40% smaller and the average exergy efficiency is approximately 35% higher.

Environmental sustainability must be considered as the main target of humanity. To achieve this goal, the activities of many people must change into pro-environmental behaviour. This is often difficult because it involves high costs, giving up some daily habits and getting out of an artificial comfort. In this sense, education has an essential role to play. Young people are the target group for which appropriate methods must be found to help raise awareness of environmental issues and their involvement in solving them. In the current situation, under the restrictions caused by the Covid-19 pandemic, practical applications with large groups of students and observation of the wild environment is difficult to achieve. In November 2020, the Department of Mechanical and Environmental Sciences within the Maritime University of Constanta organized online the activity “S.O.S. Nature” where different environmental processes have been highlighted through simulation programs. The event aimed to increase the awareness of young people about environmental pollution and its consequences, as well as stimulating transversal skills by high school students participating. The interest given by the large participation in this event and the knowledge gained in this activity underlined the importance of modelling and simulation as useful tools through whose comprehensive approach young people can understand complex environmental issues.

In accordance with the present energetic exigencies, the energy consumption in port buildings is of a vital importance. From this perspective, heat pumps are less pollutant and more energy efficient options than the traditional heating technologies. This study focuses on an air source heat pump (ASHP), operating in an administration office located in Constanta harbor, Romania, in order to supply heated water during December of 2020. Electrically driven heat pumps are seen as a successful alternative to classical expensive heating means, such as electrical heating or the one based on fossil fuels combustion. Within this research, are investigated influences of the heated water temperatures and exterior air temperatures on the theoretical Coefficient of Performance, the compression ratio and the discharge temperature. The cycle is working with R134a, with 50C superheating and sub cooling. It will be considered that the heated water is supplied in the range (40-50) 0C, while the outdoor air temperature varies in the range (0-10) 0C. Obtained results show that the highest efficiency of the ASHP is obtained for the lowest value of the heated water temperature and for the highest value of the outdoor air temperature. This situation corresponds also to the good working of the compressor of the refrigeration plant, since are seen lowest values of the compression rate and the discharge temperature, as well. This means that the compressor do not consume high amounts of energy and the oil is not damaged because of high temperatures of the refrigerant vapors.

This paper evaluates the indoor temperature and thermal sensation inside the naturally ventilated small-medium size, historical Anadolchioi Mosque, built in Constanta, in 1870, for the Muslim minority living in Constanta. Are considered Friday prayers (Dhuhr). The methodology used for this assessment is related to the outdoor and indoor temperatures measurements, each Friday, in July, between 10 AM and 4 PM, due to the fact that in Constanta, Friday prayers (in July) starts between 1.20 PM and 1.23 PM (depending on the sun position). The measurements will indicate that, although indoor temperature is slightly higher than the outdoor one, the average indoor temperature, for the considered period, is in the recommended thermal comfort temperature range, according to ASHRAE 2010. Also, the measured indoor air temperatures and predicted temperature for comfortable indoors- given by Humphreys formula, have been compared, in order to have an idea if the building is able to provide pleasant indoor temperatures. On the other hand, the methodology is focusing on ASHRAE seven point scale, when assessing the thermal sensation. In this respect, a survey regarding the thermal sensation of the occupants indicated that a low percent (5.55%) felt uncomfortable during the religious services. The majority of occupants (77.77%) felt comfortable and do not need a cooler environment. The results are in concordance with the participants’ age profiles: older persons preferring higher indoor temperatures.

The purpose of this paper is to investigate the possibility of using NRM30 in order to replace R22, in existing plants on board the ships. NRM30 is a refrigerant mixture of R134a/R1270/RE170 (55/37.5/7.5 by mass percentage). This approach is based on the better environmental behaviour of NRM30. The comparison between R22 and NMR30 has been developed on the basis of Coefficient of Performance (COP), temperature at compressor exit, power consumption per ton of refrigeration and volumetric refrigeration capacity variations, when evaporation temperature and condensation temperature increase. The above mentioned are calculated when the evaporation temperature varies in the range (-2, +10)° C and the condensation temperature varies in the range (40, 50)° C. The results reveal that COP increases with the increase of the evaporation temperature and the decrease of the condensation temperature- for both refrigerants. Although the ecological refrigerant (NRM30) shows an average COP value lower than the one of R22 (about 30% lower), NRM30 ensures an ecological operation of the plant and lower temperatures at compressor exit- which it is benefic for the long life of this machine. For the considered temperature ranges, the plant operates in efficient conditions for the higher value of the evaporation temperature (+10°C) and for the lowest value of the condensation temperature (40°C). For this conditions, it is seen that the vapours temperatures at the compressor exit are lowest, being ensured also the safe operation of the compressor.

Contaminants met during marine transportation erode air compressor blades of the gas turbine; the result of this process is sein in the decrement of the performance and the increment of fuel need. Also, there is an energy degradation during the operation of the gas turbines, being required an exergy analysis which is able to provide a plan for this power plant performance enhancement. This paper is discussing the benefits brought by nanotechnology when improving the energy efficiency in gas turbines, more specifically applying erosion resistant nanocoatings to compressor air foils is a way to optimize gas turbine performance. Ceramic matrix composites ensure durability of the components under high operating temperatures. Besides the technology dealing with better coats, the exergy analysis assesses the waste of potential energy – also known to be exergy destruction. Exergy destruction has an impact on the efficiency of the plant; moreover each component part of the thermal system has a contribution to the merit of the gas turbine. This is why are formulated exergy destructions for these components. According to the results of this analysis, it can be stated that the least inefficient component of the gas turbine system is the compressor, followed by the gas turbine itself. The object of this study is a 4,1 MW gas turbine with ceramic matrix composites nanocoating, operating at different loads (60%, 80%, 100%).

Nanorefrigerants are a new class of refrigerants, resulted by adding nanoparticles in a conventional refrigerant. Vapor compression refrigeration systems play an important role in refrigeration applications, which are sein to be one of the most energy consuming technologies. Improving energy efficiency of these systems is a nowadays challenge, due to environmental benefits. On the other hand, the use of ecological refrigerants (ODP=0 and low GWP) is an actual trend, in accordance with international regulations. This paper focuses on the performance of a vapor compression system in two cases: when the working fluid is a pure refrigerant (R600a) and when the working fluid is a nanorefrigerant (R600a/Al2O3). The nanorefigerant has resulted by adding Al2O3 nanoparticles the environmental friendly refrigerant R600a. The results indicate that the system working with the nanorefrigerant has an enhanced performance; also, it is investigated its behavior when keeping the evaporation temperature constant and the condensation temperature varies.

The most significant concerns related to vapour compression refrigeration systems (VCRS) refer to environmental behaviour and energy efficiency. The present study is taking into consideration the refrigerant R600a due to its very good thermodynamic properties and environmental position. On the other hand, the maximum performance of such a system will be identified by the help of the laws of thermodynamics. This is due to the fact that the analysis based exclusively on the energy analysis will not reveal where the performance of the system is degraded and how intense. After the formulation of the specific mathematical background, within the analysis have been varied the evaporation temperature in the range (–22, –8) ° C. Exergy losses in the main components of VCRS were assessed; the energy and exergy efficiencies of VCRS – as well. Resulted that the system is working at its highest efficiency for the highest evaporation temperature considered: for te = –8°C, the energy efficiency is 2,7 while the exergy efficiency is 55%. The most inefficient component part was found to be the compressor, while the most efficient is the evaporator. Such an analysis is very useful when aiming the design, the optimization and performance assessment of VCRS.