Nano spray drying of pharmaceuticals

[EN] Spray drying plays a crucial role in the processing of pharmaceutical products such as pills, capsules, and tablets as it is used to convert drug containing liquids into dried powdered forms. Nano spray drying is in particular used to improve drug formulation by encapsulating active ingredients in polymeric wall materials for protection and delivering the drugs to the right place and time in the body. The nano spray dryer developed in the recent years extends the spectrum of produced powder particles to the submicron- and nanoscale with very narrow size distributions and sample quantities in the milligram scale at high product yields. This enables the economical use of expensive active pharmaceutical ingredients and pure drugs. The present paper explains the concept of nano spray drying and discusses the influence of the main process parameters on the final powder properties like particle size, morphology, encapsulation efficiency, and drug loading. Application results of nano spray drying for the formulation and encapsulation of different drugs are reviewed.Arpagaus, C. (2018). Nano spray drying of pharmaceuticals. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 611-618. https://doi.org/10.4995/IDS2018.2018.7356OCS61161

Experimental Comparison of HCFO and HFO R1224yd(Z), R1233zd(E), R1336mzz(Z), and HFC R245fa in a High Temperature Heat Pump up to 150 °C Supply Temperature

The use of industrial high-temperature heat pumps (HTHP) is particularly interesting for heat recovery applications and various industrial processes such as steam generation, drying, sterilization, paper production, or food preparation. The application of new synthetic hydrofluoroolefin (HFO) and hydrochlorofluoroolefin (HCFO) refrigerants with low environmental impact is becoming increasingly important in future HTHP. At our university in Switzerland, a laboratory-scale HTHP has been developed as part of the SCCER-EIP project (Swiss Competence Center for Energy Research – Efficiency of Industrial Processes). The developed heat pump is single-stage, operates with a variable speed piston compressor, and contains a continuously adjustable internal heat exchanger (IHX) for superheating control. A viscous POE oil (173 mm2/s at 40 °C) is used to achieve sufficient lubrication at high temperatures with the refrigerants. This paper presents the experimental performance of the HCFO and HFO refrigerants R1224yd(Z), R1233zd(E), and R1336mzz(Z) as drop-in replacements for the fluorinated hydrocarbon (HFC) R245fa in the same laboratory HTHP with 10 kW heating capacity. Starting from a reference point at W60/W110 (50 K temperature lift), a parameter study was performed to investigate the operating maps (i.e. heating capacity and COP) of the heat pump in the range from 30 to 80 °C heat source and 70 to 150 °C supply temperature. Besides, an overview of the thermophysical, environmental, and safety aspects of the refrigerants is given. At W60/W110 COPs of 3.2, 3.1, 3.0, and 3.1 for R1224yd(Z), R1233zd(E), R1336mzz(Z) and R245fa were measured. Up to about 110 °C, R1224yd(Z), R1233zd(E), and R245fa presented a slightly higher COP than R1336mzz(Z) due to higher heating capacities and lower relative heat losses at the same temperature conditions. Due to higher critical temperatures, R1336mzz(Z) was more efficient at 150 °C heat supply temperature. Otherwise, the differences in COP were within the measurement uncertainty of maximum ± 0.22 COP. The integration of the IHX in the heat pump cycle significantly increased the COP and the heating capacity over the entire operating map compared to a basic cycle. A further COP increase was achieved by a higher temperature glide on the heat supply side from 5 to 30 K (increased subcooling), which is promising in processes with low return temperatures. The drop-in tests also showed that the heating capacity of R1224yd(Z) was on average 9% higher than that of R1233zd(E), which in practice requires slightly smaller compressors to achieve a comparable heating capacity. Overall, the very low GWP, the non-flammability, and the negligible environmental impact (i.e. low trifluoroacetic acid (TFA) formation during atmospheric degradation) of the investigated HCFO and HFO refrigerants indicate a high potential for future use in HTHP applications and retrofit systems

Two-Stage Heat Pump using Oil-Free Turbocompressors - System Design and Simulation

The combination of multi-stage heat pump cycles with small-scale oil-free turbocompressor technology running on gas bearings could be a promising way to increase performance in domestic and commercial heat pumps. This paper presents a novel two-stage heat pump system with two heat sources at two different temperature levels using two separate turbocompressors rotating on gas bearings optimized for R134a. The system allows integration of unused heat sources, e.g. solar thermal or waste heat, into heat production with a minimal loss of exergy. The cycle comprises an evaporator for the first heat source, a condenser as heat sink, an open economizer with integrated heat exchanger for the second heat source, and a tube-in-tube suction line heat exchanger (SHX) in the high-pressure for superheating and subcooling. The aim of this study is to evaluate theoretically the performance of this heat pump cycle using a system model programmed in the software EES (Engineering Equations Solver). The simulation assumes steady-state, negligible pressure drops and heat losses, and adiabatic expansion processes. The superheating in the evaporator and the SHX is 5°C, and there is no subcooling in the condenser. The heat exchangers are modeled using effectiveness-NTU models. At the design point, the heating capacity of the condenser is set to 6.5 kW and provides hot water of 55°C. The first heat source is brine of 5°C. The second heat source is water of 30°C and has been designed to provide up to 30% of the total condenser heat capacity. The two turbocompressors are designed specifically to meet the heat pump design point. Presently, one-dimensional (1D) compressor maps are used in the heat pump model. Simulation results show that coefficient of performance (COP) improvements of 20% to 30% are achievable, depending on the source temperature levels of the heat pump cycle and the amount of second heat source added to the system. The COP increases with higher source temperatures, higher second heat source capacity, and lower sink temperature. The pressure ratios are defined by the imposed temperature levels. The mass flow rate of the refrigerant in the first stage is mainly determined by the second heat source capacity, and in the second stage by the heat capacity of the condenser. In future work, this novel heat pump concept will be tested experimentally

Multi-Temperature Heat Pumps - A Literature Review

Reducing primary energy consumption by utilizing heat recovery systems has become increasingly important in industry. In many sectors, heating and cooling is required at different temperature levels at the same time. For this purpose, heat pumps are highly attractive energy conversion devices. Heat pumps are widely used for refrigeration, air-conditioning, space heating, hot water production, heat upgrading, or waste heat recovery. The aim of this paper is to review the literature for mechanical driven heat pumps and refrigeration systems with focus on multi-temperature applications. Different design strategies are presented, including cycles with multi-stage compressors, (multiple) ejectors, expansion valves, cascades (with secondary loops), and separated gas coolers. This review highlights the major advantages, challenges, and industrial applications of each multi-temperature heat pump cycle family. Schematics and pressure-enthalpy diagrams illustrate the most promising cycles. The performance of the cycles is compared in terms of First Law efficiency (COP) and Second Law efficiency (exergy) using simplified thermodynamic simulations. The literature reveals that the major part (approximately 70%) of multi-temperature heat pump applications are found in refrigeration, i.e. supermarket food cooling, household fridges/freezers, and cooling/air-conditioning/storage during transportation. In contrast, studies on multi-temperature heating applications are rather rare with the exception of space floor heating and hot water production. Most multi-temperature cycle designs use two heat sources or two heat sinks. Heat pumps with more than three stages are not common, except for natural gas liquefaction. In supermarket applications, multiple compressors with transcritical CO2 are an established key technology. Cascades with secondary loops are another frequently applied system, mostly in the USA. Cycles with multiple ejectors are ready to market and seem to be a promising modification for system performance improvement. Ejector cycles in refrigeration and air-conditioning systems are still under development. Expansion valve cycles are an established technology in household refrigeration. Separated gas coolers for space and hot water heating have recently attracted attention due to the possible combination with supercritical CO2 cycles. Overall, this review paper serves to select the most appropriate multi-temperature heat pump cycle for a specific application

Small, High-Speed, Oil-Free Radial Turbo-compressors for Cooling Applications: Refrigerant Selection

Demand for heating and cooling continues to grow as populations and living standards continue to increase around the globe. At the same time, persistent uncertainty in energy prices and increasing awareness of the environmental impacts associated with the use of fossil fuels - including climate change and poor air quality - are motivating an interest in reducing energy use, in general, and fossil energy, in particular. Heat pumps with scroll or reciprocating compressors have been gaining ground for residential, commercial and industrial heating and cooling applications on a scale up to several tenths of kWmech (over 100 kWtherm). They usually reduce energy use relative to conventional approaches (e.g. fossil-fuel heating in conjunction with electrically-driven cooling) but require higher first costs. Micro-centrifugal compressors with impeller diameters as small as 10-20 mm operating at rotational speeds exceeding 100,000 rpm are now feasible. They are assembled with precisely machined components and they are driven directly (i.e. without gears) by efficient high-speed motors. They have impellers suspended without contact with solid surfaces through bearings lubricated by refrigerant vapor. Thus, they realize high efficiencies and eliminate well-known disadvantages resulting from the use and management of conventional lubricants in positive-displacement systems such as having to: i) ensure adequate lubricant circulation (especially for two stage systems), so as to prevent lubricant depletion at the compressor and associated increased wear and lubricant accumulation in heat exchangers (especially cold evaporators) and associated reduced rates of heat transfer (especially from enhanced surfaces); and ii) limit the maximum operating temperature of high-temperature heat pumps, so as to maintain long-term lubricant chemical stability. HFO-1336mzz(Z) (CF3CH=CHCF3) is a hydro-fluorolefin with a normal boiling point of 33.4 oC and an A1 safety classification (non-flammable, lower toxicity) according to ASHRAE standard 34. It has an ultra-low global warming potential over a 100 years of 2, which virtually eliminates business risk from climate protection regulations emerging around the world and allows R&D investments for technology development. It has been commercialized for use as a component in R-514A, a replacement for HCFC-123 in centrifugal chillers, as a working fluid for high temperature heat pumps and Rankine power cycles and as a foam expansion agent. This paper proposes novel heat pump systems based on micro-centrifugal compressors for selected heating and cooling applications, discusses refrigerant selection, evaluates the performance of systems with HFO-1336mzz(Z) as the refrigerant and identifies promising applications with potentially attractive economics for further development

Design of Oil-Free Turbocompressors for a Two-Stage Industrial Heat Pump under Variable Operating Conditions

Pair of mechanically driven turbocompressors running on gas lubricated bearings have been designed for a two-stage heat pump application functioning under variable operating conditions. Novelty in the present two-stage heat pump system lies in the application of oil-free turbocompressor technology and the introduction of unused secondary heat from various sources. Managing the operational deviations and the secondary heat during off-design heat pump operation is challenging for the turbocompressors. The turbocompressors can potentially exceed their operating range defined by the surge and choke margins, and the maximum rotational speed limit set by the structural and rotordynamic considerations. A wide operating range is, therefore, a prerequisite design condition for the turbocompressors. The present paper will guide the readers through different stages of the design process of such turbocompressors subjected to various constraints. Moreover, a stochastic evaluation on the influence of variable operating conditions on the heat pump and turbocompressor performance will be detailed

High Temperature Heat Pumps: Market Overview, State of the Art, Research Status, Refrigerants, and Application Potentials

This study reviews the current state of the art of high temperature heat pumps (HTHPs) with heat sink temperatures of 90 to 160°C. The focus is on the analysis of heat pump cycles, suitable refrigerants, and the operating ranges of commercially available HTHPs and heat pumps at the research status. More than 20 HTHP models from 13 manufacturers have been identified on the market that are able to provide heat sink temperatures of at least 90°C. Only a few heat pump suppliers have already managed to exceed 120°C. Large application potentials have been recognized particularly in the food, paper, metal, and chemical industries, especially in drying, pasteurizing, sterilizing, evaporation, and distillation processes. The heating capacities range from about 20 kW to 20 MW. The refrigerants used are mainly R245fa, R717, R744, R134a, and R1234ze(E). Most circuits are single-stage and differ primarily in the applied refrigerant and compressor type. Internal heat exchangers (IHX) are used to ensure sufficient superheating. Process optimization is achieved with economizer cycles or two-stage turbo compressors with intermediate vapor injection. Two-stage cascade cycles or open flash economizers are also used in commercial HTHPs. The COP values range from about 1.6 to 5.8 at temperature lifts of 130 to 40 K, respectively. Several research projects push the limits of the achievable COPs and heat sink temperatures to higher levels. Groups in Austria, Germany, France, Norway, the Netherlands, Switzerland, Japan, Korea, and China are active in the experimental research of HTHPs. Several laboratory scale HTHPs have been built to demonstrate the technical feasibility of sink temperatures above 120°C. The heat pump cycles examined are mainly single-stage and in some cases contain an IHX for superheating or an economizer for vapor injection into the compressor. The investigated refrigerants are R1336mzz(Z), R718, R245fa, R1234ze(Z), R600, and R601. R1336mzz(Z) enables exceptionally high heat sink temperatures of up to 160°C. The experimentally obtained COPs at 120°C heat sink temperature vary between about 5.7 and 6.5 at 30 K temperature lift and 2.2 and 2.8 at 70 K lift. New environmental friendly refrigerants with low GWP and improved components lead to a need for research on optimized cycles. The high level of research activity and the large number of demonstration R&D projects indicate that HTHPs with a heat sink temperature of 160°C will reach market maturity in the next few years. However, despite the great application potential, other competing heating technologies and most importantly low prices for fossil fuels are still hindering the wider spread of HTHPs in industry

Simulation of a VRF system applied in elcectric buses in Taiwan

Based on test data from an electric bus manufacturer, HVAC systems will consume nearly 30% of the available energy in fully electrically operated public transport buses, which heavily decreases the bus mileage. Therefore, improvements for the bus HVAC system structure are needed. In contrast to conventional electric bus HVAC systems, a VRV (variable-refrigerant-volume) system will be simulated as HVAC system. The compressors provide adequate power depending on the requirements from the different heat exchanger units inside the bus cabin. This system will provide either cooling or heating capacity depending on the needs of the target space. Therefore, the energy consumption of the compressors will be reduced This paper will present a dynamic EES simulation model of a VRV system applied in an electric public transportation bus. Goal of this simulation is, to simulate and design the specifications of the VRV HVAC system with given system performance requirements. The bus model and the simulation results will be described in detail in this publication. This project has been developed in collaboration between the Automotive Research and Testing Center of Taiwan (ARTC) and the University of Applied Sciences in Buchs (NTB)