Installation of potable water supply and heat supply at base of subsoil water

This is an O Abstract. Removal of groundwater with further use of it for potable water supply and heat supply with the use of heat pump is an important problem. A new revolutionary approach to the decision of energy and water saving that provides rational accommodation of groundwater boreholes ensuring the required flow rate of water through the heat pump evaporator with simultaneously high intensity of heat exchange process is proposed. The method of calculation which allows determining the necessary depth of borehole, quantity of boreholes, in consideration of flow rate and temperature of subsoil water determining capacity of heat pump installation is worked out.


Introduction
Numerous regions of the world are under negative influence of subsoil water circulating near surface of the ground.That is why the purpose of the work is to estimate the prospects of implementation of the installation for removal of subsoil water from houses for further supply of potable water and heat to consumers at the base of heat pump [1].This task is especially important in the autumn-winter period for regions with high level of subsoil water when danger of flooding of the buildings is grown considerably and deficiency of energy for heating increases simultaneously [2][3][4][5].

A general material
We offer new revolutionary approach to the decision of this task that provides rational accommodation of subsoil water boreholes supporting the required flow rate of water for thermal needs of heat pump evaporator with high intensity of heat exchange process simultaneously.The circuit of heat pump installation with integrated purposes (preventing flooding of buildings during a high-water period of time, heat and potable water supply) at base of subsoil water includes a borehole circuit and water purification circuit.Heat pump installation of potable water and heat supply at base of subsoil water has a special module for water purification [6].
Installation of potable water and heat supply (Fig. 1) at base of heat pump 3 includes the evaporator 5, compressor 6, condenser 7 and throttle gate 8. Evaporator 5 is placed in the circuit of circulation of subsoil water incoming from borehole 1 via pump 2. Condenser is placed in the circuit of circulation of heat consumer 10.The system of water purification 4 includes subsoil water tank 11, incoming through evaporator 5, water pump 12, module of purification with tanks 13, 14 and pump 15 for potable water supply of consumers 16.

Results and discussion
Results of numerical simulation (Figs. 2 and 3) shows that flow rate of subsoil water is close to square-law dependence on pressure z = H 0 À h 0 , because of laminar mode of flow of subsoil water through the ground layer.Flow rate of subsoil water depends proportionally on filtration factor f but influence of borehole's radius r 0 is negligible.Figure 2 allows determining necessary depth of borehole = 0 with the account of h 0 and quantity of boreholes (at changes of borehole depth).
For heat pump evaporator having surface area of heat transfer F = 320 m 2 , having heat transfer coefficient k f = 0.5 kWh/(m 2 K) for temperature difference Dt = 6 °C, which corresponds to the heat flow density q = 3 kW/m 2 .
The heat power (Fig. 3) of the evaporator can be defined as: For the case of cooling of subsoil water in the evaporator of heat pump Dt w = 10 °C the required flow rate of subsoil water, with the account of equation ( 2), can be defined as: The temperature of the refrigerant boiling in the evaporator of heat pump can be estimated as [9]: where Ethermodynamic efficiency, which show the ratio of real flow of heat to maximum possible in the ideal heat exchanger.
In our case C w = C min , therefore: From equation (4): where for evaporator of the heat pump [10].
In order to estimate the cost-effectiveness of the installation the method of economic evaluation based on a comparison of cost of the traditional heat supply unit and traditional water supply unit was applied [11][12][13] .
Results of numerical simulation shows that in case of three boreholes (for example, for loam) when the depth of each borehole is 60 m the flow rate of subsoil water equals G w = 7.6 Â 3 = 22.8 kg/s (Fig. 2).Temperature of boiling of refrigerant (R-142) equals 1.5 °C; temperature of condensation of refrigerant equals 70 °C; temperature of hot water 65 °C; efficiency of compressor 0.85; flow rate of refrigerant equals 7.3 kg/s; COP = 3.5; heat capacity of condenser of heat pump equals 1350 kW; electric capacity of electric motor for compressor equals N K = 390 kW; heat capacity of heat pump evaporator equals 960 kW, capacity of 3 electric motors for subsoil water pump equals 16 kW.While heat capacity of heat pump equals Q h = 1350 kW, the quantity of apartments which can be supplied by heat equals 450 (needs of one apartment approximately 3 kW) [14].
The total economic efficiency of heat and water supply system can be determine with the account of annual costs of heat supply system Z y h and water supply system Z y w (e.g.G w = 22.8 kg/s) [13]: where C y h ; C y wannual operating costs of heat and tap water production; K h , K wcosts of the system (including costs of heat pump, boreholes with water pumps and water supply system with water treatment installation); Е nnormative amortization factor (Е n = 0.1).
Annual operating costs for the generation of heat: where C h el À cost of 1 kWh; t y = 8760annual operating hours; nnumber of persons serving the installation; Z nmonthly salary per person; N h elelectric power for generation of heat.
where N kelectric capacity of electric motor of compressor; N elelectric power of water pump.Annual costs for heat generation: Specific costs for heat production: Annual operating costs for the generation of pure water: where N w el ¼ 30kWelectric power for pumps of water treatment unit.
Annual costs for water supply system: Specific costs for water provision in case of three boreholes: where z sp ws ¼ 0:1 USD=m 3costs of pure water.Cost savings due to implementation of water provision system while T = 10 years of operation: Cost savings due to implementation of heat provision system while T = 10 years of operation: General cost savings due to implementation of installation of heat and potable water supply at base of heat pump while T = 10 years of its operation can be defined as: Dz ¼ Dz h Dz w ¼ 810 Â 10 3 450 Â 10 3 ¼ 1:26 Â 10 6 USD:

Conclusions
Removal of subsoil waters from the surface of the ground with its subsequent use for water and heat supply reduces negative influence of subsoil waters circulating near to surface of the ground.Especially during autumn-winter period in the regions with high level of subsoil water a danger of flooding of the buildings becomes real and deficiency of energy for heating rises simultaneously.Heat pump installation with integrated purposeswater and heat supplycan compensate escalating annually deficiency of potable water for numerous regions having problems with water deficit and allows solving the problem of substitution of traditional fuels.
Social effect of implementation of heat pump installation with integrated modes of workpreventing flooding of buildings during a high water period.
The results of numerical simulations show technical and economic expediency of application of heat pump installation with integrated purposes.The general economy while 10 years equals 1.26 Â 10 6 USD (including water provision -0.45 Â 10 6 USD, heating 0.81 Â 10 6 USD).
The amount of specific investments into heat pump systems is largely determined by the applied technology and quantity of heat and water derived from the utilization of subsoil water.In general, the specific costs decrease with an increase in integrated capacity of system.