Open loop , heat pump

Open-loop systems. Groundwater is pumped from a borehole (or mine shaft) and circulated directly through the heat pump, which extracts heat directly from the water. This method is obviously appropriate where a significant water yield, with a suitable quality, can be achieved and maintained. 

Use closed-loop systems, which might be installed down-mine , or within settlement basins at a minewater treatment plant. Here the collector fluid circulates in a closed-loop and never comes into contact with the mine water. Likewise, mine water never enters the heat pump or heat exchanger elements. The problem is thus wholly averted, although there are limitations in capacity to closed-loop systems. For larger capacity operations, open systems will be preferred. Furthermore, the exterior of such closed-loop systems may become heavily fouled, necessitating periodic removal for cleaning. 

Where open-loop systems are unavoidable, mine water should be circulated through heat pumps and exchangers in such a way as to minimize contact with atmospheric Oz, which promotes oxidation of Fe2+ to poorly soluble Fe3+. Also consideration should be given to pressurized systems, in which down-mine pressures are maintained as far as possible, to hinder degassing of, for example, C02. Such degassing may elevate pH and promote precipitation of Fe-oxyhydroxides or carbonate scales. 

The practical implementation of the above policies is not necessarily as straightforward as solving the above equations. As can be deduced from Equations 6.70-6.76, Pjjjj is a function of the propagation rate coefficients, the monomer concentrations, and most importantly, the total radical concentration. Hence, to precalculate the optimal monomer feed rates, the radical concentration must be specified in advance and kept constant via an initiator feed policy and/or a heat production policy. This is especially important considering that a constant radical concentration is not a typical polymer production reality. This raises the notion that one could increase the reactor temperature or the initiator concentration over time to manipulate the radical concentration rather than manipulate the monomer feed flowrates, that is, keep P j constant for simpler pump operation. Furthermore, these semibatch policies provide the open-loop or off-line optimal feed rates required to produce a constant composition product. The online or closed-loop implementation of these policies necessitates a consideration of online sensors for monomer... 

Figure 10.2.6. Open-loop heat-pump arrangement for binary distillation in a single column.

In burn-out experiments, a test section is part of a loop which may be open or closed, and the question arises as to whether or not any of the loop equipment, such as condensers, heaters, pumps, or pipe fittings, have any significant effect on the burn-out flux. This issue came to prominence at the Boulder Heat Transfer Conference in 1961 with a Russian paper by Aladyev (A4) describing burn-out experiments in which a branch pipe, connecting to a small vessel, was fitted close to the test section inlet. The test section itself was a uniformly heated tube 8 mm in diameter and 16 cm long. The results are reproduced in Fig. 9, and show burn-out flux plotted against exit steam quality. Curve (A) was obtained with the branch vessel filled with cold water,... 

The concept of a transfer-line booster station is similar, but it utilizes a receiver or flash dewar having a pump with a sump-type inlet. Boost pumping w ould serve a wasteful purpose if it relayed unavailable energy (as sensible heat) in two-phase flow to the propellant tank. Use of the flash tank opens the loop of the transfer-system piping to vent the vapor that would otherwise carry over. The scaled-down design and development of such a system follows. 

The primary, secondary and tertiary heat transfer system, and the emergency core cooling system were set to 400°C isothermal, the primary coolant loop dampers to minimum opening and the main pumps with the pony motors to 5% nominal speed. The flow-rate in the emergency core cooling rtused by means of the electromagnetic pumps to 100%,... 

---