Judul: Sebaran diameter pohon sengon, Paraserianthes falcataria (L>) Nielsen yang mendapat serangan Xystocera festiva Pascoe pada berbagai umur tegakan
Abstrak: Pohon sengon [Paraserianthes falcataria (L) Nielsen] merupakan salah satu jenis pohon unggulan dalam program pembangunan hutan tanaman dan hutan rakyat di Indonesia khususnya di Pulau Jawa. Salah satu masalah dalam pengusahaan hutan sengon adalah adanya serangan hama pengerek batang Xystrocera festiva Pascoe (Coleoptera; Cerambycide) yang banyak dikenal dengan nama boktor sengon. Adanya sejumlah lubang gerek pada batang menyebabkan penurunan kualitas dan kuantitas kayu pertukangan yang dihasilkan. Penelitian ini bertujuan untuk menentukan pola serangan Xystrocera festiva Pascoe menurut diameter pohon pada berbagai umur tegakan sengon [Paraserianthes falcataria (L) Nielsen]. Hasil penelitian ini diharapkan dapat digunakan dalam pelaksanaan penjarangan tegakan sengon yang telah mengalami serangan boktor sengon (Xystrocera festiva Pascoe).
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Judul: Populasi larva dan banyaknya lubang gerek Xystrocera festiva Pascoe pada berbagai umur tegakan sengon (Paraserianthes falcataria (L) Nielsen
Abstrak: Salah satu spesies pohon andalan adalah Paraserianthes falcataria atau sengon. Masalah yang paling umum dihadapi dalam pengusahaan hutan tanaman sengon adalah serangan hama penggerek batang Xystrocera festiva atau dikenal juga dengan nama boktor sengon. Penelitian ini bertujuan untuk mengetahui populasi larva Xystrocera festiva dan banyaknya lubang gerek per pohon dan per hektar pada berbagai umur tegakan sengon. Data jumlah larva dan lubang gerek Xystrocera festiva ini dapat dimanfaatkan dalam pengendalian hama.
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Judul: Exergy Analysis of Membrane Utilization for Solution Separation in LiBr-H2O Absorbtion Refrigeration System
Abstrak: Absorbtion refrigeration system provides prominent advantages in tems of environmental impact and energy consumption. Absorbtion refrigeration system uses natural refrigerant, such as water, which gives no harm to the environment. In terms of energy consumption, it requires heat to regenerate refrigerant from its absorber and provide the refrigeration effect. This form of energy is preferred since heat can be supplied from various sources, including waste heat and renewable energy, and thermodynamically categorized as low quality energy. However, effectiveness of refrigerant regeneration could only be obtained if the temperature is high enough. In this study, the heat utilization in the regeneration process will be eliminated by introducing membranes for separating the refrigerant from the absorber. Specifically, the objectives of this research are to :1) to study the absorbtion mechanism of water vapor by LiBr-H2O solution in a controlled condition, 2) to study the regeneration process of LiBr-H2O using reverse osmosis (RO) membrane and vacuum membrane distillation (VMD) when applied in LiBr-H2O absorbtion refrigeration system, 3) to perform the energy and exergy analysis in LiBr-H2O absorbtion refrigeration system using RO membrane. The membrane was used as a tool to separate the refrigerant from absorbent which performs as regeneration process in conventional absorbtion system. As separation component, RO membrane employs pressure to oppose the osmotic pressure and pass certain component through the pores. While, VMD employs vacuum pressure and thermal, so that the substance to be transported through the membrane is in form of vapor. The result shows that absorbtion rate of water vapor by LiBr-H2O solution was influenced by solution concentration, temperature, humidity and pressure. The highest absorbtion rate was 0.031 g/minute which was occurred at temperature 40°C, RH 70% and solution concentration 60%. Prediction model was developed to calculate the absorbtion parameter inspite of P-T-X diagram.The highest water vapor absorbtion in absorber using spiral wound module-based RO membrane occurred at initial concentration of 30%, wich is the highest concentration used in the experiment. Increasing of operation pressure during separation process will increase permeation flux but decrease rejection factor.Unexpectedly, permeate of the RO membrane still contain LiBr at concentration 7w/w %-9w/w%, which affect the achievable cooling temperature and cooling capacity. Optimization of regeneration using VMD was conducted with response surface methodology (RSM) and the result show that highest permeate flux (0.93 kg.m-2.s-1) can be achived at initial concentration of 47.5%, temperature of 80°C and flow rate of 1.9 L.min-1.COP obtained in absorbtion refrigeration system using RO membran with initial concentration 20% was in the range of 1.147-1.171. Exergy analysis shows that increasing pressure of RO membrane at concentration 20% increased the irreversibity.On the other hand, exergy analysis on VMD shows that higher concentration and temperature will increased irreversibility.
Keyword: refrigeration, absorbtion, reverse osmosis, vacuum membrane distillation, energy, exergy