Journal of Sustainable Energy

3

Authors: CÂRLAN M., CSUZI. I., COSTEA M

The paper presents three operative models whose purpose is to improve the practice of preventive maintenance to a wide range of technical installations. Although the calculation criteria are different, the goal is the same: to determine the optimum time between two consecutive preventive interventions. The optimum criteria of these models are: - the maximum share of technical entity operating probabilities, in the case of the Ackoff - Sasieni [1] method; -the optimum time interval for preventive verification depending on the preventive-corrective maintenance costs imposed by the deciding factor, for the AsturioBaldin [2] model; - the minimum number of renewals – preventive and/or corrective maintenance operations [3].

5

Authors: BUZATU G. C., STAN IVAN F. E., MIRCEA P.M., MIRCEA I

The paper is structured in three parts. In the first part of the paper, are presented some theoretical notions regarding the sound, noise, the sound insulations materials. Also in the first part of the paper are presented some characteristic regarding the insulation materials and there effects. In the second part it is described an calculation example for a homogeneous wall with double structure in order to determine the attenuation index curve "Ri(f)". The example calculation contains 10 steps that must be followed and the final results are presented in table 7 and figure 3. The last part of the paper is represented by conclusions, where the authors tried to explain the importance of the curve "Ri(f)" for reducing the noise in the buildings.

6

Authors: DINU R.C., POPESCU D.

Currently, many building managers record complaints from homeowners regarding the indoor climate. The main issue is that some rooms never have the desired temperature. After changing the load, room temperatures vary, particularly at small and medium loads. The design capacity can not be transmitted during the start of the heating system after setting and operation under a week-end or night. Such problems arise when the installation has an incorrect heat flow which prevents proper functioning of regulators. Considering that flow and pressure regulators ensure effective control when flows prevail in the plant project, this paper presents two solutions with differential pressure in heating with radiators. These solutions consist in the use of automatic differential pressure regulators or proportional relief valves.