Mechanical Vapour Compression Heat Pump Research Articles

Energetic, entropic and economic analysis of a heat pump coupled humidification dehumidification desalination system using a packed bed dehumidifier

In this paper, the humidification dehumidification (HD) desalination system, driven by a mechanical vapor compression heat pump (MVCHP), is proposed. The direct contact dehumidifier, with packings filled, is applied to condense the humid air for water producing. On the basis of the thermodynamic laws, the energetic and entropic analysis, with the modified effectiveness to describe the heat and mass transfer characteristics of humidification, are first achieved to assess the desalination performance of the combined system. The influence laws from the terminal temperature difference (TTD) of the evaporator, the pressure ratio (PR) during compression and pinch temperature difference (PTD) of the condenser on the desalination performance are also explored and presented. The research results presented that the top thermodynamic performance of the MVCHP coupled HD desalination system arises as 71.56 kg h−1 for the water production, 5.28 for the gained-output-ratio (GOR) and 1.73 kJ kg−1 K−1 for the specific entropy generation rate, while two fully coupled cases at 1.21 and 1.96 for the mass flow rate ratio will emerge. It is found that water production can be elevated effectively through increasing the pressure ratio, while the peak value of GOR keeps at the design conditions. Furthermore, the positive effects from lower values both for the TTDe and PTDcon on the performance of the MVCHP coupled HD desalination system are proved. After the economic analysis, it is calculated that the cost of fresh water is about 0.018 $ L−1 with a lifetime of 10 years. According to the performance comparison, the great potential of energy conservation for the MVCHP coupled HD desalination system are validated, although the water production will be reduced after the integration of the MVCHP.

Thermodynamic Analysis of A Novel Humidification Dehumidification Desalination System Driven by Heat Pump

In this paper, the humidification dehumidification (HDH) desalination system using a packed bed dehumidifier, with a mechanical vapor compression heat pump integrated, is proposed, and the condenser is coupled to raise the seawater temperature while the evaporator is applied to absorb the energy from the discharged brine as much as possible. For the proposed combined desalination system, the mass and energy balance equations are constituted, and then the corresponding thermodynamic performance at the design conditions, both for the desalination and heat pump unit, is obtained. The simulation results show that the peak values for the water production and gained-output-ratio (GOR) emerge as 76.40kgh-1 and 5.14 at the design conditions. Compared to the general HDH desalination system, the elevation magnitudes reach ΔGOR=1.69 and 2.86 at the same conditions.

Ethanol Fermentation Coupled with Pervaporation by Energy Efficient Mechanical vapor Compression

Abstract Ethanol production could be enhanced with ethanol removal in situ from the broth, during the experiments of ethanol fermentation coupled with pervaporation by mechanical vapor compression. The yeast cell could continuously grow for long time with cell density of 38 g/L obtained. The byproducts accumulation in the broth led to the culture deterioration of the fermentation and became the main inhibitor against the cell growth. The total flux of the polydimethylsiloxane (PDMS) membrane was in the range of 350 g/m 2 /h and 600 g/m 2 /h. At the downstream of the membrane, part of the permeate vapor under the vacuum condition before the inlet of the vacuum pump was condensed at the first condenser by the running water at the room temperature and the non-condensed vapor enriched with ethanol was compressed to the atmospheric pressure and pumped into the second condenser by the vacuum pump. The vapor in the second condenser was easily condensed into a liquid by air at room temperature since the pressure was increased. Ethanol concentration of over 50wt% could be obtained in the second condenser, which could greatly reduce the amount of the waste water treatment. Recovery of the permeate vapor heat would be achieved by the use of mechanical vapor compression heat pump, which could evidently save energy.

Pervaporation membrane bioreactor with permeate fractional condensation and mechanical vapor compression for energy efficient ethanol production

Improved process separation factor and heat integration are two key issues to increase the energy efficiency of ethanol production in a pervaporation membrane bioreactor (PVMBR). A PVMBR with permeate fractional condensation and mechanical vapor compression was developed for energy efficient ethanol production. A condensation model based on the mass balance and thermodynamic equilibrium in the partial vacuum condenser was developed for predicting the purification performance of the permeate vapor. Three runs of ethanol fermentation-pervaporation experiment were carried out and ethanol concentration of higher than 50wt% could be achieved in the final condensate, with the separation factor of the process for ethanol increased to 20. Ethanol production could be enhanced in the bioreactor and 17.1MJ of the energy could be produced in per liter of fermentation broth, owing to 27.0MJ/kg heating value of the recovered ethanol. Compared with the traditional pervaporation process with low temperature condensation for ethanol production, 50% of the energy would be saved in the process. The energy consumption would be further reduced, if the available energy of the permeate vapor was utilized by integrating the mechanical vapor compression heat pump.

Experimental research of an integrative unit for air-conditioning and desalination

Desalination with a humidification–dehumidification process has proven to be an efficient means of utilization the condenser and evaporator of heat pump to product fresh water from sea water. This paper presents an integrative device of air-conditioning and desalination driven by mechanical vapor compression heat pump. There were four circuits in this system such as vapor compression, heat water, air flow and fresh water circuit. According to different combination, several function including air-conditioning, dehumidification and desalination could be realized. Compared with traditional desalination device, the system utilized the heat from condenser and cold from evaporator of heat pump adequately, and reclaimed latent heat partially. The experimental results show that it would circulate with considerably higher PER under the optimal choice of sea water flow rate, feed water temperature, the volume of sea water in box and the length of humidifier. When this system was used as dehumidification, it can regulate air temperature of outlet in a large range.

Steady-State Simulation of Air to Water Mechanical Vapour-Compression Heat Pump for Different Refrigerants)

Steady-State Simulation of Air to Water Mechanical Vapour-Compression Heat Pump for Different Refrigerants)

Alternative heat pump working fluids to CFCs

CFC-11, CFC-12, CFC-114 and HCFC-22 are used as mechanical vapour compression heat pump working fluids for low and high temperature applications. Because of the Montreal Protocol, alternative heat pump working fluids to CFCs have to be identified and developed. This paper discusses the various potential alternatives screened from various families of compounds. HFC-134a is the most popular choice as an alternative to CFC-12, although HFC-152a appears to be a better alternative. Among the HFEs, HFE-134 is a potential long-term alternative. HFC-143 and HFE-134 appear to be attractive as substitutes for CFC-114 for high temperature applications. For centrifugal compressor applications, HCFC-123 is currently the most popular choice as an interim alternative to CFC-11. HFC-245ca and HFC-143 are also potential long-term substitutes for CFC-11. The various implications with respect to these alternatives are discussed.

Developments in geothermal energy in Mexico—part thirty-six. The commissioning of a heat pump assisted brine purification system

Any system which extracts useful energy from a geothermal source is limited by the effectiveness of the heat transfer between the geothermal fluid, which has a tendency to scale, and the relevant components of the system. A heat pump can be used to maintain a temperature difference between two vessels containing pure water and geothermal brine which is sufficient to enable pure water vapour to flow continuously from the geothermal brine vessel to the pure water vessel. A mechanical vapour compression heat pump using R114 as the working fluid and designed to deliver more than 50 kW of heat has been incorporated in a brine purification system at the Los Azufres geothermal field. This system has been successfully commissioned and is operating as designed and theoretically predicted.

Heat pump assisted distillation. VIII: Design of a system for separating ethanol and water

A heat pump assisted distillation system has been designed for the separation of ethanol from 7 per cent aqueous mixtures to produce 93 per cent ethanol by weight. The distillation column has been designed on the basis of conventional design procedures. Valve trays were chosen to provide operational flexibility. R114 was chosen as the working fluid for the mechanical vapour compression heat pump. The heat pump system has been designed to match the heat loads determined for the column. Auxiliary heat exchangers have been provided to aid flexibility and control of column operation.

Heat pump assisted distillation. II: Matching an external heat pump to a fractional distillation system

The problems in matching an external mechanical vapour compression heat pump to a distillation process in heat pump assisted distillation are discussed. There are four main design parameters to consider when selecting a working fluid for the heat pump, of which only two are independent. Various arrangements for imperfectly matched systems are presented, including the use of a two stage heat pump. A number of other factors which affect the choice of a heat pump assisted distillation system, including economic factors, are also considered.

Operating characteristics of a water-to-water mechanical vapour compression heat pump using R114: Part II—Statistical analysis of the effect of lifetime and the individual operator of the heat pump

An analysis of the operating characteristics obtained by four different experimentalists over a period of about five years on a water-to-water mechanical vapour compression heat pump was made. The analysis showed that there was no significant difference between the four sets of results. The heat pump used in the study was still in the acceptance region of operation. The analysis showed that there is a small acceleration in the decrease in values of (COP) A with gross temperature lift ( T CO− T EV) through that period included in the analysis. The analysis also showed that superheats in the range 5 to 10°C, for the four sets gave both minimum error and minimum deviations between the sets.

Operating characteristics of a water-to-water mechanical vapour compression heat pump using R114: Part I—Interaction between dependent and independent parameters

The interactions between the independent parameters and the dependent parameters for a specially designed water-to-water heat pump have been studied experimentally. The independent parameters studied were working fluid flow rate, water flow rate to condenser, water flow rate to evaporator, temperature of water to condenser, and temperature of water to evaporator. The effect of the variations of these independent parameters on the dependent parameters including condensing temperature, condenser load, compressor load and coefficient of performance are presented.

Comparison of theoretical rankine heat pump cycle performance data for twenty-one working fluids

The compression ratio (CR) is largely determined by the choice of compressor in a mechanical vapour compression heat pump system. The condensing temperature T CO is largely determined by the required temperature of the heat to be delivered. This means that for a given working fluid, the theoretical Rankine coefficient of performance (COP) R and the gross temperature lift ( T CO − T EV ) are determined automatically. The only way that the values of (COP) R and ( T CO − T EV ) can be varied is to choose another working fluid. Of the twenty-one working fluids for which comprehensive thermodynamic data are available, only ten have critical temperatures high enough to be considered for use in heat pump systems with a condensing temperature of 120°C and only five can be considered for a condensing temperature of 160°C. Values of (COP) R and ( T CO − T EV ) are listed for compression ratios (CR) of 3, 4, 5 and 6 for condensing temperature T CO of 100, 120 and 160°C respectively.