Pump cycle

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. 

Figure 6 9 The grand composite curve can be used to size heat pump cycles. (From Smith and Unnhoff, Trans. IChemE, ChERD, 66 195, 1988 reproduced by permission of the Institution of Chemical Engineers.)...

A wide variety of metliods has been used to pump laser systems. Altliough optical pumping has been implied, tliere is an array of collisionally or electron impact pumped systems, as well as electrically pumped metliods. The efficiency of tire pumping cycle in many ways defines tire utility and applications of each scheme. The first... 

Feng Zhou, Andreas Windemuth, and Klaus Schulten. Molecular-dynamis study of the proton pump cycle of bacteriorhodopsin. Biochem., 32(9) 2291-2306, 1993. 

Active carbons can be used in both refrigeration and heat pumping cycles, but their potential for use in these applications does not necessarily merit the development of such systems. Before devoting research and development effort into active carbon-based thermodynamic cycles, the interest in both heat-driven cycles in general, and adsorption cycles in particular, must be justified. 

Methyl radicals were produced by pyrolysis of azomethane (CH3N2CH3). Azomethane was synthesized as describe earlier [18]. It was purified periodically by fteeze-pump cycles at 77 K, and the gas purity verified by RGA. The methyl radical source was similar to that developed by Stair and coworkers. [10, 11] The source was made of a quartz tube with 3 mm OD and 1 mm ID, resistive heating was supplied by means of a 0.25 mm diameter tantalum wire wrapped outside the quartz tube. The len of the heating zone was 4 cm, recessed from the end of the tube by 1 cm. An alumina tube around the outside of the heating zone served as a radiation shield. Azomethane was admitted to the hot tube at a pressure of 1x10-8 to 1x10-7 Torr via a high-vacuum precision leak valve. The pyrolysis tube was maintained at about 1200 K, adequate to decrease the major peaks in the mass sp trum of the parent azomethane at 58 and 43 amu by at least a factor of 100. 

Chemical heat pump uses chemical reaction for thermal energy storage and conversion. The heat pump operation is based on reaction equilibrium relationship, and has two operation modes. Figure 221 shows equilibrium relationship of chemical heat pump cycle for Mg0/H20 system at (a) heat amplification and cooling mode and (b) heat transformation mode [26], Figure 222 shows... 

Figure 221. Equilibrium relationship of chemical heat pump cycle for MgO/EFO system (a) heat amplification and cooling mode, (b) heat transformation mode...

The distance between the injection-pumping wells should be such that approximately six injection-pumping cycles can be completed within a six-month period. 

Figure 16.38 The grand composite curve allows heat pump cycles to be sized.

In the single-headed reciprocating pump shown in the figure, the mobile phase is being delivered to the column for only half of the pumping cycle. During the drive stroke of the piston, the flow rate is not constant (because the speed of the piston changes with time). The output of the pump is shown in Fig. 2.2e (z). Use of a twin-headed pump with the two heads operated 180° out of phase... 

Temperature Two modes of temperature parametric-pumping cycles have been defined—direct and recuperative. In direct mode, an adsorbent column is heated and cooled while the fluid feed is pumped forward and backward through the bed from reservoirs at each end. When the feed is a binary fluid, one component will concentrate in one reservoir and one in the other. In recuperative mode, the heating and cooling takes place outside the adsorbent column. Parametric pumping, thermal and pH modes, have been widely studied for separation of liquid mixtures. However, the primary success for separating gas mixtures in thermal mode has been the separation of propane/ethane on activated carbon [Jencziewski and Myers, Ind. Eng. Chem. Fundam., 9, 216-221 (1970)] and of air/S02 on silica gel... 

Patrick, Schrodt, and Kermode, Sep. Sci, 7, 331-343 (1972)]. The difficulty with applying the thermal mode to gas separation is that in a fixed volume gas pressure increases during the hot step, which defeats the desorption purpose of this step. No thermal parametric-pumping cycle has yet been practiced commercially. 

For the concentration of fruit juice by evaporation, it is proposed to use a falling-film evaporator and to incorporate a heat-pump cycle with ammonia as the medium. The ammonia in vapour form enters the evaporator at 312 K and the water is evaporated from the juices at 287 K. The ammonia in the vapour—liquid mixture enters the condenser at 278 K and the vapour then passes to the compressor. It is estimated that the work required to compress the ammonia is 150 kJ/kg of ammonia and that 2.28 kg of ammonia is cycled/kg water evaporated. The following proposals are made for driving the compressor ... 

The pumping rate of the lower pump is adjusted to produce sufficient water to cause a cone of depression extending outward to intercept and retrieve the LNAPL. While the water pump operates continually, the upper product pump cycles on and off as necessary to recover the product as it accumulates. 

The evaporation of citrus juices at temperatures up to 328 K, or of pharmaceutical products at even lower temperatures, has led to the development of an evaporator incorporating a heat-pump cycle using a separate working fluid. The use of the heat pump cycle, with ammonia as the working fluid is shown in Figure 14.13. In this arrangement, ammonia... 

Figure 14.13. Heat pump cycle using ammonia...

The use of a heat pump cycle is the subject of Problem 14.22 at the end of this Volume, and a detailed discussion of the topic is given in the Solutions Manual. 

Carnot Refrigerator and Heat Pump Basic Vapor Refrigeration Cycle Actual Vapor Refrigeration Cycle Basic Vapor Heat Pump Cycle Actual Vapor Heat Pump Cycle Working Fluids for Vapor Refrigeration and Heat Pump Systems Cascade and Multistaged Vapor Refrigerators... 

Thermodynamic cycles can be divided into two general eategories heat engine cycles, which are discussed in Chapters 2-5, and refrigeration and heat pump cycles, which are discussed in Chapter 6. 

The Carnot cycle is a reversible cycle. Reversing the cycle will also reverse the directions of heat and work interactions. The reversed Carnot heat engine cycles are Carnot refrigeration and heat pump cycles. Therefore, a reversed Carnot vapor heat engine is either a Carnot vapor refrigerator or a Carnot vapor heat pump, depending on the function of the cycle. 

Does the area enclosed by the Carnot heat pump cycle on a T-s diagram represent the network input for the heat pump ... 

Does the Carnot heat pump cycle involve any internal irreversibilities ... 

The T-s diagram of the basic vapor heat pump cycle, which consists of the following four processes, is shown in Fig. 6.10 ... 

Determine the COP, horsepower required, and heating load of a basic vapor heat pump cycle using R-134a as the working fluid and in which the condenser pressure is 900 kPa and the evaporation pressure is 240 kPa. The circulation rate of fluid is O.lkg/sec. Show the cycle on a T-s diagram. Plot the sensitivity diagram of COP versus condenser pressure. 

Figure 6.11a Basic vapor heat pump cycle.

The actual vapor heat pump cycle deviates from the ideal cycle primarily because of inefficiency of the compressor, pressure drops associated with fluid flow and heat transfer to or from the surroundings. The vapor entering the compressor must be superheated slightly rather than a saturated vapor. The refrigerant entering the throttling valve is usually compressed liquid rather than a saturated liquid. 

Determine the COP, horsepower required, and heating load of a basic vapor heat pump cycle using R-134a as the working fluid and in which... 

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