Heat recovery refrigeration in New Zealand dairy sheds : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Agricultural Engineering at Massey University

Increased energy costs initiated an investigation into refrigeration heat recovery as one conservation alternative available for reducing water heating costs on farm dairies. A theoretical energy balance was conducted, from which the potential of recovering refrigeration condenser heat was estimated at up to 60% of the water heating energy requirements. Preliminary tests with heat exchangers lead to the use of a tube-in-tube, counter flow, heat exchanger with fins on the refrigerant side, and cores on the water side, to improve the heat transfer characteristics. The exchanger, designed to provide 300 litres of 60°C water from a 2.25 kw refrigeration system cooling 2000 litres of milk per day, had an area of 0.84 m2, and an overall thermal conductance of 100 W.m-2.°C-1. This heat exchanger was inserted between the compressor and condenser of the refrigeration plant and tested with two condenser systems (air and water), four condenser pressures (6.5 bar, 7.5 bar, 10 bar and 12 bar), two milk inlet temperatures(23°C and l8°C), and two milk final temperatures (4°C and 7°C). In addition, tests on receiver pressure and suction superheat were performed to determine overall system performance. Increasing condenser pressure increased cooling times from 2 hours 32 minutes to 3 hours 17 minutes, after the completion of the 1200 litre morning milking (thus failing to comply with the 3 hour cooling regulation at high condenser pressures.) Also, C.O.P. decreased from 3.05 to 2.35 for the water cooled condenser system (2.70 to 2.00 for the air cooled condenser system due to fan power consumption). Gross heat recovery rose from 4.2 kWh.day-1 .m-3 to 8.l kWh.day-1 .m-3 for the water cooled system, giving water outlet temperatures of 45°C to 64°C as condenser pressure rose. The corresponding ranges for air cooled condensers were 3.8 kWh.day-1 .m-3, to 6.6 kWh .day-1 .m-3, and 38°C to 55°C. Changing milk inlet and final temperatures gave a proportional change in cooling times and total heat recovery, but had no effect on C.O.P. or heat recovery rates. Suction superheating increased total heat recovery by 15%, and water outlet temperatures by 9%. Increases in gross heat recovery with increasing condenser pressure were partially offset by additional compressor power, and yielded nett heat recoveries of 4.0 kWh.day-1 .m-3 to 6.0 kWh.day-1 .m-3 for water cooled, and 3.6 kWh. day-1 .m-3 to 4.3 kWh. day-1 .m-3 for air cooled, condenser systems. The maximum gross and nett heat recoveries (at 12 bar condenser pressure) were applied to the energy requirements of a monitored 220 cow town supply dairy. This analysis showed that the gross heat recovery was 51% of the water heating requirements, but the nett heat recovery dropped to 17% of the total heating and refrigeration demand. Based on current electricity and equipment prices, it is estimated that the payback period for this level of recovery would be 16-17 years. Changing the electricity pricing structure, to reflect up to a 1:3 differential in favour of water heating power costs, results in the 6.5 bar condenser pressure giving optimum results, but the nett returns are significantly lower than those reported. The potential for improved savings is greater from larger capacity systems as the capital investment is not proportionally increased with an increase in scale

Оснащение конденсаторов паровых турбин системами шарикоочистки охлаждающих труб и дополнительной очистки охлаждающей воды

Представлено матеріали по оснащенню конденсаторів парових турбін системами кулькоочистки охолоджуючих труб та додаткової очистки охолоджуючої води.Materials by fitting out of steam-turbine condenser by systems of ball cleaning cooling tubes and after purification cooling water are present

Radiation-cooled Dew Water Condensers Studied by Computational Fluid Dynamic (CFD)

Harvesting condensed atmospheric vapour as dew water can be an alternative or complementary potable water resource in specific arid or insular areas. Such radiation-cooled condensing devices use already existing flat surfaces (roofs) or innovative structures with more complex shapes to enhance the dew yield. The Computational Fluid Dynamic - CFD - software PHOENICS has been programmed and applied to such radiation cooled condensers. For this purpose, the sky radiation is previously integrated and averaged for each structure. The radiative balance is then included in the CFD simulation tool to compare the efficiency of the different structures under various meteorological parameters, for complex or simple shapes and at various scales. It has been used to precise different structures before construction. (1) a 7.32 m^2 funnel shape was studied; a 30 degree tilted angle (60 degree cone half-angle) was computed to be the best compromise for funnel cooling. Compared to a 1 m^2 flat condenser, the cooling efficiency was expected to be improved by 40%. Seventeen months measurements in outdoor tests presented a 138 % increased dew yield as compared to the 1 m^2 flat condenser. (2) The simulation results for 5 various condenser shapes were also compared with experimental measurement on corresponding pilots systems: 0.16 m^2 flat planar condenser, 1 m^2 and 30 degree tilted planar condenser, 30 m^2 and 30 degree tilted planar condenser, 255 m^2 multi ridges, a preliminary construction of a large scale dew plant being implemented in the Kutch area (Gujarat, India)

Pengaruh Beban Pendinginan terhadap Temperatur Sistem Pengkondisian Udara Hibrida dengan Kondensor Dummy Tipe Trombone Coil Menggunakan Pipa Tembaga Berdiameter 1/4" sebagai Water Heater

The hybrid air conditioning systems can improve the energy efficiency by recovering waste heat of condenser that can be useful for various purposes. There are many experimental studies about this system which aimed to investigate and improve the energy efficiency. This experimental study aims to investigate the effect of cooling loads to system temperatures of hybrid air conditioning with trombone coil type of dummy condenser using 1/4″ diameter of copper pipe as water heater. The system has been tested with several cooling loads as residential cooling load simulation, such as 0 Watt, 1000 Watt, 2000 Watt, and 3000 Watt. The result shows that the maximum water temperature is obtained at 47.30 ˚C with average discharge temperature of 105.45 ˚C in 3000 Watt cooling load after 120 minutes of operation. The more the cooling load applied to simulation room, the more the temperatures of water and discharge increased

Optimum dry-cooling sub-systems for a solar air conditioner

Dry-cooling sub-systems for residential solar powered Rankine compression air conditioners were economically optimized and compared with the cost of a wet cooling tower. Results in terms of yearly incremental busbar cost due to the use of dry-cooling were presented for Philadelphia and Miami. With input data corresponding to local weather, energy rate and capital costs, condenser surface designs and performance, the computerized optimization program yields design specifications of the sub-system which has the lowest annual incremental cost

Cooling load forecasting-based predictive optimisation for chiller plants

Extensive electric power is required to maintain indoor thermal comfort using heating, ventilation and air conditioning (HVAC) systems, of which, water-cooled chiller plants consume more than 50% of the total electric power. To improve energy efficiency, supervisory optimisation control can be adopted. The controlled variables are usually optimised according to instant building cooling load and ambient wet bulb air temperature at regular time intervals. In this way, the energy efficiency of chiller plants has been improved. However, with an inherent assumption that the instant building cooling load and ambient wet bulb temperature remain constant in the coming time interval, the energy efficiency potential has not been fully realised, especially when cooling loads vary suddenly and extremely. To solve this problem, a cooling load forecasting-based predictive optimisation method is proposed. Instead of minimising the instant system power according to the instant building cooling load and ambient wet bulb temperature, the controlled variables are derived to minimise the sum of the instant system power and one-time-step-ahead future system power according to both instant and forecasted future building cooling loads. With this method, the energy efficiency potential of a chiller plant can be further improved without shortening the operation time interval. 80% redundant energy consumption has been reduced for the sample chiller plant; energy can be saved for chiller plants that work for years. The evaluation on the effect of cooling load forecasting accuracy turns out that the more accurate the forecasts are, the more redundant energy consumption can be reduced

Heat tube device

The present invention discloses a heat tube device through which a working fluid can be circulated to transfer heat to air in a conventional air conditioning system. The heat tube device is disposable about a conventional cooling coil of the air conditioning system and includes a plurality of substantially U-shaped tubes connected to a support structure. The support structure includes members for allowing the heat tube device to be readily positioned about the cooling coil. An actuatable adjustment device is connected to the U-shaped tubes for allowing, upon actuation thereof, for the heat tubes to be simultaneously rotated relative to the cooling coil for allowing the heat transfer from the heat tube device to air in the air conditioning system to be selectively varied

A Multiscale Thermo-Fluid Computational Model for a Two-Phase Cooling System

In this paper, we describe a mathematical model and a numerical simulation method for the condenser component of a novel two-phase thermosyphon cooling system for power electronics applications. The condenser consists of a set of roll-bonded vertically mounted fins among which air flows by either natural or forced convection. In order to deepen the understanding of the mechanisms that determine the performance of the condenser and to facilitate the further optimization of its industrial design, a multiscale approach is developed to reduce as much as possible the complexity of the simulation code while maintaining reasonable predictive accuracy. To this end, heat diffusion in the fins and its convective transport in air are modeled as 2D processes while the flow of the two-phase coolant within the fins is modeled as a 1D network of pipes. For the numerical solution of the resulting equations, a Dual Mixed-Finite Volume scheme with Exponential Fitting stabilization is used for 2D heat diffusion and convection while a Primal Mixed Finite Element discretization method with upwind stabilization is used for the 1D coolant flow. The mathematical model and the numerical method are validated through extensive simulations of realistic device structures which prove to be in excellent agreement with available experimental data

Cooling system for high speed aircraft

The system eliminates the necessity of shielding an aircraft airframe constructed of material such as aluminum. Cooling is accomplished by passing a coolant through the aircraft airframe, the coolant acting as a carrier to remove heat from the airframe. The coolant is circulated through a heat pump and a heat exchanger which together extract essentially all of the added heat from the coolant. The heat is transferred to the aircraft fuel system via the heat exchanger and the heat pump. The heat extracted from the coolant is utilized to power the heat pump. The heat pump has associated therewith power turbine mechanism which is also driven by the extracted heat. The power turbines are utilized to drive various aircraft subsystems, the compressor of the heat pump, and provide engine cooling

Extruder for food product (otak–otak) with heater and roll cutter

Food extrusion is a form of extrusion used in food industries. It is a process by which a set of mixed ingredients are forced through an opening in a perforated plate or die with a design specific to the food, and is then cut to a specified size by blades [1]. Summary of the invention principal objects of the present invention are to provide a machine capable of continuously producing food products having an’ extruded filler material of meat or similarity and an extruded outer covering of a moldable food product, such as otak-otak, that completely envelopes the filler material