Development and optimization of a method for analyzing biodiesel mixtures with non-aqueous reversed phase liquid chromatography

Biodiesel (a mixture of fatty acid esters) is normally analyzed using gas chromatography/flame ionization detection, as specified by the ASTM D6584 and EN14105 standards. This paper proposes a binary gradient method for analyzing biodiesel mixtures using non-aqueous reverse phase HPLC with a UV detector capable of overcoming the drawbacks of the gas chromatographic technique normally used. The new analytical method was developed by means of a statistical sensitivity analysis applied to the main parameters influencing the recording, using the full factorial design method combined with the Yates algorithm and the steepest ascent optimization procedure. The present study shows the influence of the main biodiesel mixture separation analysis parameters. The resulting tool proved valid for analyzing not only biodiesel but also any traces of unreacted oil

Demand Side Management analysis of a commercial Water Loop Heat Pump system

Demand side management (DSM) can be defined as a set of measures adopted to modify customers\u2019 energy demand with the aim of improving the efficiency of the overall energy system. Indeed, DSM strategies can be used to reduce customers\u2019 demand at peak times, reduce energy consumption seasonally/yearly, change the timing of end-use consumption from high to low-cost periods, and increase consumption during off-peak periods. DSM strategies can be implemented by using the energy flexibility available in the final users\u2019 applications, e.g. the thermal inertia of the building mass, the presence of additional energy storage systems enabling load shaping or the use of control systems to turn on/off end-users\u2019 devices when required. Being intensive energy consumers because of a high electric energy demand (mainly for refrigeration, which accounts for about 40 % of the yearly energy consumption), supermarkets are ideal candidates for energy use optimizations obtained through a DSM approach. This work shows the results of a DSM analysis carried out for a refrigeration and HVAC plant in a supermarket coupled with a Water Loop Heat Pump (WLHP) system. The water loop is used as a heat source/sink for the refrigeration unit supplying the cooling capacity required by food preservation and for several heat pumps that provide heating/cooling inside the supermarket building. The system is modelled in TRNSYS and the role of the water loop and its thermal inertia to provide energy flexibility is investigated. The system design and control strategy are modified in order to reduce the electricity costs in presence of demand response programs based on real-time price mechanisms

Potential Impacts of the Montreal Protocol Kigali Amendment to the Choice of Refrigerant Alternatives

The paper first gives a description of the “ Kigali Amendment” established HFC phase-down as decided by the Montreal Protocol parties in Kigali, Rwanda, October 2016. Baselines, freeze dates, schedules for the reductions of HFC consumption for both developing and developed country groups, as well as the 17 HFCs that are now included in the Montreal Protocol are summarized. The list of alternatives for HCFC- 22 including high-GWP HFC replacements is given, and considerations regarding the choice of refrigerant, both low-GWP synthetic and “natural” refrigerant alternatives are presented. The low-GWP refrigerant flammability issue and the performance of equipment at high ambient regions are described. It is discussed whether the potential impacts of the Kigali Amendment will be reinforcing the momentum of applications using low-GWP refrigerants and the innovation for sustainable RACHP technologie

innovative coupling of cogeneration units with fire tube boilers thermo fluid dynamics of the fire tubes

Nowadays the thermal energy demand in the industrial sector is usually satisfied by means of fire tube boilers while electricity is supplied from the grid. Alternatively cogeneration units could be adopted for thermal and electrical energy self-production, whilst installing boilers only as back-up units. However, even when cogeneration is profitable, it is not widespread because industries are usually unwilling to accept cogeneration plants for reliability and high investment costs issues. In this work a system aimed at overcoming the above mentioned market difficulties is proposed. It consists of an innovative coupling of a combined heat and power unit with a modified fire tube boiler. In particular, a CFD analysis was carried out by the authors in order to address the most critical aspects related with the coupling of the two systems. More precisely, the following aspects were evaluated in detail: (i) pressure losses of the exhausts going from the prime mover to the boiler due to the sudden cross-section area variations; (ii) thermal power recoverable from the exhausts in the tubes of the boiler; (iii) dependence of the system on the final users' specification