Aqueous solutions of organic or inorganic salts are used as secondary refrigerants in indirect refrigeration systems to transport and transfer heat. Water is known for its corrosive character and secondary refrigerants based on aqueous solutions have the same tendency. The least corrosive from the aqueous solutions are glycols and alcohols. Salt solutions, such as chlorides and potassium salts, are much more corrosive. Nevertheless, it is possible to minimize corrosion risks at the beginning stage while designing system. Proper design can significantly help in improving system performance against corrosion. There are several aspects which need to be taken into account while working with secondary refrigerants: design of system, selection of secondary refrigerant, proper corrosion inhibitors, compatible materials used to build the installation and proper preparation of system to operation. While choosing proper materials it is advised to avoid the formation of a galvanic couple to reduce the risk of the most dangerous type of corrosion. Oxygen present in installation is another important factor increasing the rate of corrosion. Even small amounts of oxygen can significantly affect the system lifetime. The methods of cleaning, charging the system with refrigerant, and deaeration procedures are extremely important. The purpose of this thesis work is to present the problems of corrosion occurring in the indirect systems with secondary refrigerants. The thesis describes the mechanism of corrosion and its different types, most commonly used materials in installation, different corrosion inhibitors used to protect system. This thesis also lists the available secondary refrigerants on the market and briefly describes them. Further, it describes the important aspects related with designing, preparing and maintaining of indirect systems. This thesis is giving some clues and shows what should be done in order to reduce risks of corrosion. / Effsys 2 P2 project

Hydraulic development engineers and tribology specialist still exert substantial effort, time and resources into finding a hydraulic fluid that would be near an ideal fluid. In addition to its basic physicochemical properties, it must meet a number of other requirements related to its practical use within hydraulic system and the materials used therein. Ionic Liquids, as novel lubricants, offer the solution in this regard. The paper gives an overview of the basic properties of selected and tested Ionic Liquids suitable for use as hydraulic fluids. The practically obtained data refer to the basic physico-chemical properties of Ionic Liquids and properties important for practical use within hydraulic system, e.g. compatibility with materials. The results are given in a comparison with common mineral oil based hydraulic oil.

An implantable closed-loop insulin delivery device (INsmart device) containing a glucose responsive gel has been developed within the INsmart research group, over a period of 10 years, to mimic pancreas. In this thesis, the reliability and performance capability of the INsmart device was studied for future clinical use. Investigations into the device material compatibility with insulin solution, assessed by monitoring insulin loss and degradant formation over a period of 31 days using RP-HPLC have shown that stainless steel and titanium are the most compatible materials. Polycarbonate contributes to insulin loss after 11 days, resin might not be the best material and polyurethane is the least compatible for future device designs. To study insulin delivery mechanism and kinetics from the device, fluorescently labelled human insulin (FITC-insulin) was synthesised and characterised using RP-HPLC and MS, to produce a product with predominantly di-labelled conjugate (>75%) with no unreacted FITC or native insulin. Clinically used insulin analogues were also fluorescently labelled to produce predominantly di-labelled FITC-insulin conjugate with potential future biological and in vitro applications. The drug release mechanism from the glucose sensitive gel held in the INsmart device, studied using fluorescein sodium was determined as a Fickian diffusion controlled release mechanism. The diffusion coefficient (D) for FITC-insulin in the non-polymerised dex2M-conA gel (NP gel) determined using mathematical models, QSS and TL slope methods was 1.05 ± 0.02 x 10-11 m2/s and in the cross-linked dex500MA-conAMA gel (CL gel) was 0.75 ± 0.06 x 10-11 m2/s. In response to physiologically relevant glucose triggers in the NP gel, the diffusivity of FITC-insulin increases with increasing glucose concentrations, showing a second order polynomial fit, device thus showing glucose sensitivity and graded response, mimicking pancreas. Rheological measurements further confirmed the gel glucose responsiveness demonstrated by a third order polynomial fit between FITC-insulin D and the NP complex viscosity in response to increasing glucose concentration. The knowledge of FITC-insulin diffusion kinetics in the gel has aided in making some theoretical predictions for the capability and performance of the INsmart device. Alternate device geometry and design optimisation is also explored.