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The Heat Pump

The coefficient of performance, rj, of a refrigerator is the ratio of the heat extracted from the low-temperature reservoir to the work destroyed  [Pg.163]

The coefficient of performance is the heat extracted from the cold box for each unit of work expended. From Eq. (8.24) it is apparent that as T2, the temperature inside the cold box, becomes smaller, the coefficient of performance drops off very rapidly this happens because the numerator in Eq. (8.24) decreases and the denominator increases. The amount of work that must be expended to maintain a cold temperature against a specified heat leak into the box goes up very rapidly as the temperature of the box goes down. [Pg.163]

Suppose we run the Carnot engine in reverse, as a refrigerator, but instead of having the interior of the refrigerator serve as the cold reservoir we use the outdoors as the cold reservoir and the interior of the house as the hot reservoir. Then the refrigerator pumps heat, Q2, from outdoors and rejects heat, — 6u the house. The coefficient of performance of the heat pump, is the amount of heat pumped into the high temperature [Pg.163]

This remarkable formula is best illustrated by an example. Suppose that the exterior temperature is 5 °C and the interior is 20 °C. Then if — fT = 1 kJ the quantity of heat pumped into the house is [Pg.164]

If we try to assess the relative economy of a heat pump versus burning fossil fuel directly, we must bear in mind that, if the electrical energy to run the heat pump comes from fossil fuel, the power plant is subject to the Carnot limitation. The overall efficiency of a modern steam power plant is about 35 percent. Thus, just to break even on fossil fuel consumption, the heat pump coefficient of performance must be at least 1/0.35 = 2.9. [Pg.164]

One more method to decrease As consists of the apphcation of the so-called heat pump of mechanical or absorption type (Fonyo Benko, 1998). Heat, given in [Pg.279]

Heat can be passed from the condenser to the reboiler with the help of an auxiliary contour, the working body of which can be steam or hot water (Fig. 8.7a). Vapor flow, going out from the column from above (Fig. 8.7b), or liquid, going out from the column from below (Fig. 8.7c), are used as working body in the auxiluary contour in other types of heat pump. Heat pumps of absorption type, having the auxiliary system absorber-desorber, are more compUcated. [Pg.280]

The application of heat pump leads to additional capital and energy expenditures. Therefore, total economy of expenditures on separation can be achieved in such a way only if the difference Tret - Tcon) is not large (i.e., at separation of a narrow-boiling mixture). Examples of application of heat pump in industry are columns for separation of ethane and ethylene, propane and propylene, ethylbenzene and styrene, and isobutane and butane. [Pg.280]

In a number of cases, if bubble temperatures of the components of the mixture under separation are very close to each other and the structure of their molecules is different, it is profitable to use extractive distillation, even atseparation of zeotropic mixtures, to decrease energy and capital expenditures (separation of mixtures of hydrocarbons of different homologous rows). The economy of expenditures on separation is being achieved at the expense of the fact that separation of one narrow-boiling mixture is replaced by separation of two wide-boiUng mixtures in two column at extractive distillation. [Pg.280]

While synthesizing separation flowsheets, it is necessary to consider the pos-sibUity of thermodynamic improvement and thermal integration. Therefore, for each sequence, identified in the process of synthesis, it is necessary to realize possible thermodynanric improvements and thermal integration of the columns. The estimation of expenditures on separation is made taking into consideration these modifications, if these expenditures are smaller than for the sequence without modifications under consideration. This estimation of expenditures is used while comparing the sequence under consideration to all other possible sequences. [Pg.280]


Thus the appropriate placement of heat pumps is that they should be placed across the pinch. Note that the principle needs careful interpretation if there are utility pinches. In such circumstances, heat pump replacement above the process pinch or below it can be economic, providing that the heat pump is placed across a utility pinch. Such considerations are outside the scope of the present text. [Pg.204]

For any given type of heat pump, a higher COPhp leads to better economics. Having a better COPhp and hence better economics means working across a small temperature lift with the heat pump. The... [Pg.204]

Most refrigeration systems are essentially the same as the heat pump cycle shown in Fig. 6.37. Heat is absorbed at low temperature, servicing the process, and rejected at higher temperature either directly to ambient (cooling water or air cooling) or to heat recovery in the process. Heat transfer takes place essentially over latent heat profiles. Such cycles can be much more complex if more than one refrigeration level is involved. [Pg.206]

Various heat pumping schemes have been proposed as methods for saving energy in distillation. Of these schemes, use of the column overhead vapor as the heat pumping fluid is usually the most economically attractive. This is the vapor recompression scheme shown in outline in Fig. 14.6. [Pg.346]

Figure 15.4 A plant for the production of animal feed. The heat pump encroaches into a pocket in the gremd composite curve. (From Smith and Linnhojf, Trans. IChemE, ChERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)... Figure 15.4 A plant for the production of animal feed. The heat pump encroaches into a pocket in the gremd composite curve. (From Smith and Linnhojf, Trans. IChemE, ChERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)...
Equation (9-245) shows that in this particular case the fixed-capital cost per unit of input energy CpJW) must not exceed 160,000 (GJh" )" or 576 per kilowatt, to have a 1-year payback period if the heat pump is operational for 8000 h/year. For this case the corresponding value of y is about 0.12 for a heat pump with an operating life of 10 years purchased with money borrowed at a 10 percent rate of interest. [Pg.861]

For the heat pump (HP) operation, heat rejected at the high temperature (( Kigk) is the objective, thus ... [Pg.1106]

A theoretical discussion of the heat pump appeared in the Journal of the Franklin Institute in I 886. T. G. N. Haldane of Scotland comprehensively pursued the application of heat pumps to the heating of buildings after the mid-1920s. Haldane tested air-to-watcr heat pump systems in his home and concluded that... [Pg.609]

Haldane, T. G. N. (1930). The Heat Pump An Economical Method of Producing Low-Grade Heat from Electricity. Journal of the Institution of Electrical Engineers 68 666—675. [Pg.611]

Heat pumps. Both the source and sink of heat pumps can be gas or liquid. The particular feature of the heat pump is that the source is at a lower temperature than the sink and is upgraded by the heat pump. To obtain a reasonable efficiency it is essential that heat is required at a low temperature and the source and sink are close in temperature. [Pg.267]

The heat wheel The heat pipe The run-round coil The heat pump... [Pg.466]

The great benefit of the heat pump is the possibility of upgrading the heat as compared to the other methods, and is popular in swimming-pool applications, where the heat recovered from the exhaust air can be used to heat the incoming fresh air and the pool water and to provide hot water for showers and washing purposes. [Pg.466]

The most advantageous application of the heat pump in the UK at the present time is where air cooling is required in the summer and air heating from the same piece of equipment in the winter. The alternatives will be electric resistance heating, with a higher fuel cost, or the provision of a hot water coil, at extra capital cost. [Pg.320]

The economics of the heat pump are dependent on the relative costs of the drive power and heat energy from other sources. In the UK, where electricity is currently about three times the price of natural gas, the electric drive heat pump needs to have a COP of 3 to break even, and 4 or more to be competitive. This price ratio will change as fossil fuels run out in the next century. [Pg.322]

If the conditions are suitable the process fluid can be used as the working fluid for the heat pump. This arrangement is shown in Figure 3.11b. The hot process liquid at high... [Pg.110]

The same models mentioned in Section 6.3.3 can be used to heat the water. However the heat pump can be a heating only type. The capacity of the unit is sized to meet the peak load in excess of the capacity of the central heat pump at... [Pg.122]

When the temperature of the heating water falls below the design temperature during the heating season, the water stored in the tank will be released to the heating circuit. The water-to-water heat pump will maintain the temperature of stored water in the tank. The storage tank allows the heat pump water heater to operate at a lower output than the heating demand of the... [Pg.123]

Small to medium size water-to-water heat pumps are considered in this system. Since the primary pumps are common to all the heat pumps, this system may not be ideal for projects where large size multiple heat pumps are used. It is better if dedicated primary pumps are used in the case of large multiple heat pumps. This is discussed in Section 6.4.1. [Pg.124]


See other pages where The Heat Pump is mentioned: [Pg.204]    [Pg.204]    [Pg.206]    [Pg.362]    [Pg.110]    [Pg.860]    [Pg.860]    [Pg.860]    [Pg.861]    [Pg.861]    [Pg.24]    [Pg.577]    [Pg.609]    [Pg.610]    [Pg.610]    [Pg.611]    [Pg.1131]    [Pg.1132]    [Pg.320]    [Pg.322]    [Pg.145]    [Pg.77]    [Pg.15]    [Pg.16]    [Pg.112]    [Pg.116]    [Pg.122]    [Pg.124]    [Pg.124]    [Pg.126]    [Pg.129]    [Pg.159]   


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